On Christmas Eve 1781, Mozart and Clementi engaged in a piano duel in the presence of Emperor Joseph II and the visiting Grand Duchess of Russia, Maria Fyodorovna. It is one of the most famous events in the lives of both musicians, yet its documentary sources have never been carefully evaluated. The only eye-witness account from the time is Mozart’s own, in letters to Leopold written just after the contest, and on 12 and 16 Jan 1782; only the last describes the encounter in any detail. All other evidence is long after the fact, second-hand, anecdotal, or some combination of these.

The anecdote reproduced here comes from a short book published in 1827 by Giuseppe Antonio Bridi (1763–1836): Brevi notizie intorno ad alcuni più celebri compositori di musica e cenni sullo stato presente del canto italiano (Brief notes about some of the most famous composers of music and remarks on the present state of Italian singing). Brevi notizie contains short vignettes on seven composers honored by Bridi in a small “Temple of Harmony” in the garden of his estate in Rovereto: Sacchini, Handel, Gluck, Jommelli, Joseph Haydn, Palestrina, and Mozart. Bridi’s vignette on Mozart is based largely on previously published sources (Schlichtegroll’s Nekrolog, for one), and is rather careless with basic facts (Bridi has Mozart dying in 1793, for example)—but it includes two anecdotes not known from any other source. In one anecdote, Paisiello, in Vienna for several months in 1784 for the composition and premiere of Il re Teodoro in Venezia, asks Mozart to borrow the score of Idomeneo for study. Bridi then points to a passage in Paisiello’s Pirro (1787) that uses a novel musical procedure that (Bridi believed) Paisiello borrowed from Mozart’s opera (see our entry “Paisiello and Idomeneo”, with further biographical background on Bridi). Bridi’s other anecdote, on the Mozart-Clementi duel, is transcribed and translated here. The anecdote comes at the end of an extended comparison between Mozart and Raphael, who died at a similarly young age, and similarly left a prodigious body of work at the highest level. (This comparison had already been made by Friedrich Rochlitz in the Allgemeine musikalische Zeitung in 1800; AmZ, no. 37, 11 Jun 1800, cols. 641–51.)

The key passages in Mozart’s letters describing the duel were first published in Nissen’s Mozart biography in 1828. But Bridi’s Brevi notizie appeared the previous year, and it is unlikely that he knew Mozart’s description of the duel. Bridi’s anecdote was first cited in a footnote in the second edition of Jahn’s Mozart biography (i:638n33), but its text was first published in full in Max Unger’s biography of Clementi (Unger 1913, 30–31). Unger did not put much stock in the anecdote’s accuracy, writing that it seemed as if “der Schreiber [habe] seine Phantasie ziemlich lebhaft spielen lassen” (“the writer allowed his fantasy quite free rein”; Unger 1913, 30).

The anecdote has subsequently been mostly dismissed or ignored in the subsequent literature on both composers. Leon Plantinga writes in his biography of Clementi:

[Bridi’s] description contains so many errors of detail (the Grand Duchess is called the ‘gran Principessa delle Russie’ and the ‘Contessa del Nord’, and the Grand Duke Paul ‘Augusto’) that there seems to be little reason to take it seriously. [Plantinga 1977, 66]

Yet Plantinga is wrong on all these points and his dismissal shows a lack of acquaintance with the historical context. While Bridi’s reference to Maria Fyodorovna as “gran Principessa delle Russie” may not be precisely correct, neither is it exactly an error: the grand duchess had been born Princess Sophie Dorothea of Württemberg, adopting the Russian name upon her conversion to Russian Orthodoxy and her marriage to Grand Duke Paul of Russia; so she was indeed a princess. Mozart, in his letter to Leopold on 16 Jan 1782, refers to her as “Grosfürstin,” which can also be translated as “Grand Princess” (albeit of a different kind; Briefe, iii:193). During their tour of Europe in 1781 and 1782, the grand duke and duchess were traveling nominally incognito under the names the “Count and Countess of the North,” something that Bridi knew but Plantinga apparently did not. And Bridi certainly intended “augusto” as an adjective describing the grand duke, not as a first name: Bridi’s “coll’ Augusto suo Sposo” means “with her august husband,” not “with August her husband.” That this was Bridi’s intended meaning is emphasized by his use of the adjective twice more in the same passage: “i due augusti personaggi” (“the two august personages,” referring to the grand duchess and the Emperor) and “l’Augusta assemblea” (“the august company” listening to Clementi and Mozart). But most importantly, neither Unger nor Plantinga seems to have been aware that Bridi spent most of his working life in Vienna, was (by Mozart’s account and his own) a close friend of the composer, and sang the role of Idomeneo in the production of the eponymous opera in the theater of Prince Auersperg in 1786 (see our entry “Paisiello and Idomeneo”). Thus whatever the flaws and inconsistencies of Bridi’s vignette on Mozart, his anecdotes must be taken seriously, because he was on the scene in the 1780s and knew Mozart. As we shall see, his anecdote about the duel with Clementi is, in fact, the earliest known published account of the event to include any substantial description of it (apart from an anecdote of unknown provenance published in 1813 that differs from more credible sources in nearly every detail).

The Italian-born composer and pianist Muzio Clementi (1752–1832) had lived in England since 1766 or 1767, and in London from around 1774. In 1780 he undertook a trip to the continent that ended up lasting over three years. This period of Clementi’s life is scantily documented; most of what we know comes from a biography published in 1820 in The Quarterly Musical Magazine and Review (ii:308–16); Alan Tyson (1966, 17) attributes the biography to “Clementi’s friend and business partner,” William Frederick Collard, and it is probably based on information provided by Clementi himself. According to the 1820 biography:

⁣    [Clementi’s] reputation, without the protection of any patron, rose with
such rapidity that in a very short time he received the same remu-
neration for his instructions as J. C. BACH; and the fame of his
works and of his executive talents, having spread over the Continent,
he determined, in the year 1780, and at the instigation of the cele-
brated PACCHIEROTTI, to visit Paris.
    In that city he was received with enthusiasm, and had the honour
to play before the Queen, who bestowed on him the most unqualified
applause. The warmth of French praise, contrasted with the gen-
tle and cool approbation given by the English, quite astonished the
young musician, who used jocosely to remark, that he could
scarcely believe himself to be the same man. Whilst he remained
in that capital he composed his Operas 5 and 6, and published a
new edition of his Op. 1, with an additional fugue. Having enjoyed
the unabated applause of the Parisians until the summer of 1781, he
determined on paying a visit to Vienna. In his way there he stopped
in Strasburgh, where he was introduced to the then Prince De Deux
Ponts, the present King of Bavaria, who treated him with the greatest
distinction; and also at Munich, where he was received with equal
honour by the Elector.
[The Quarterly Musical Magazine and Review, 1820, ii:311]

According to Plantinga (1977, 59), Clementi left London sometime after 26 May 1780. Thus the biography in The Quarterly Musical Magazine and Review implies that he remained in Paris for around a year. Yet he is not known to have made any public appearances in Paris during his stay there (Plantinga 1977, 59). Our only other potential hint regarding Clementi’s time in Paris comes from Antoine Marmontel’s Les Pianistes célèbres. Silhouettes et médaillons, published in 1878. Marmontel writes:

En 1780, Clementi fit un premier voyage à Paris. [...] Admis à se faire entendre à la cour, la perfection de son jeu charma la reine Marie-Antoinette, qui lui témoigna une bienveillante sympathie, et l’engagea à visiter Vienne, en l’assurant de sa protection auprès de son frère l’empereur Joseph, le célèbre mélomane. [Marmontel 1878, 51]

In 1780, Clementi made a first trip to Paris. [...] Permitted to play before the court, the perfection of his playing charmed Queen Marie Antoinette, who showed him a kindly sympathy, and advised him to visit Vienna, assuring him of her recommendation to her brother, Emperor Joseph, the celebrated music lover.

Much of what Marmontel writes about Clementi seems ultimately to derive from one of the several versions or reprints of the Clementi biography first published in The Quarterly Musical Magazine and Review. However, his reference to Marie Antoinette does not. Unfortunately, Marmontel does not cite a source, but the story is at least plausible: it is not difficult to imagine that Marie Antoinette might have suggested to Clementi that he visit Vienna and promised that she would recommend him to her brother Joseph.

It was probably also in Paris that Clementi learned of the planned grand tour of Grand Duke Paul of Russia and his wife, Grand Duchess Maria Fyodorovna. A letter from Clementi to his father, written in Vienna on 24 Dec 1781, the day of the duel, suggests that he had timed his arrival to coincide with the Russian couple’s stay in Vienna:

In quanto a Bordeaux cambiai di sentimento quando i miei amici mi proposero di venire subito qui dove ci si trova adesso il Gran Duca di Russia, ma di dove partirà ben presto per fare il giro d’Italia. Sono cinque giorni ch’io sono arrivato quà, e sta sera [sic] avrò l’onore d’essere introdotto alla Gran Duchessa che vuol sentirmi sul cembalo. [Plantinga 1980, 71, transcription amended]

As far as Bordeaux is concerned, I changed my mind when my friends suggested that I come here immediately, since the Grand Duke of Russia is here just now, but will quite soon be leaving to make a tour of Italy. It is five days since I arrived here, and this evening I shall have the honor to be introduced to the Grand Duchess, who wishes to hear me on the cembalo. [Plantinga 1977, 61, translation amended]

(Plantinga 1977 gives a photo of the first page of the letter in his plate 5, between pages 82 and 83.)

According to the biography in The Quarterly Musical Magazine and Review, Clementi stopped in Strasbourg and Munich on his way to Vienna. His arrival in Munich on 15 Nov 1781 is recorded in the Münchner wöchentliche Anzeigen:

After leaving Munich, Clementi spent several days in Regensburg, where his arrival on 30 Nov is recorded in the Regensburgisches Diarium (Tue, 4 Dec 1781, 389; see Haberl 2012, 181). According to the diary of ambassador Marquis Marc-Marie de Bombelles, Clementi gave concerts in Regensburg on 7 and 9 Dec (Meixner 2008, 239).

The grand duke and duchess arrived in Vienna on 21 Nov 1781 and departed on 4 Jan 1782 (see our entry for 8 Oct 1782; the couple visited Vienna a second time in Oct 1782). Clementi writes on 24 Dec 1781: “It is five days since I arrived here…”, thus placing his arrival in Vienna around 19 Dec. Clementi’s statement that the grand duchess desired to hear him is consistent with Bridi’s statement that it was she who summoned him.

Mozart refers to the competition three times in his known letters to Leopold. In a letter begun on 22 Dec 1781, but finished and sent on the 26th, after the competition had taken place, Wolfgang writes:

[...] — und vorgestern als den 24:ten habe ich bey hofe gespielt — es ist noch ein clavier spieller hier angekommen, ein Welscher er heist. Clementi. dieser war auch hineinberufen. — gestern sind mir davor 50 Duccaten geschickt worden; welche ich dermalen recht nöthig brauche. — [...]
[Briefe, iii:188]

[...] — and the day before yesterday, the 24th, I played at court — another keyboard player has come here, an Italian named Clementi. He was also summoned. — Yesterday 50 ducats were sent to me for this, which I need quite badly right now. — [...]

The “50 Duccaten” were probably “kaiserlich” (imperial) ducats, at that time worth 213 fl 20 kr (at a rate of 4 fl 16 kr per ducat). Mozart does not say whether he knew ahead of time that he would be competing with Clementi, and Clementi’s letter to his father does not mention Mozart, only that Clementi would be playing for the grand duchess. The implication would seem to be, then, that neither knew in advance what was in store for him; this is also consistent with Bridi’s anecdote.

Mozart refers to the competition again briefly and indirectly in a letter to Leopold on 12 Jan 1782:

der Clementi spielt gut, wenn es auf execution der rechten hand ankömmt. — seine force sind die terzen Paßagen — übrigens hat er um keinen kreutzer gefühl oder geschmack. mit einem Wort ein blosser Mechanicus. — [Briefe, iii:191]

Clementi plays well, when it comes to execution with the right hand. His forte is passages in thirds — otherwise, he hasn’t a kreuzer’s worth of feeling or taste. In a word, a mere technician. —

But Mozart’s main description of his encounter with Clementi comes in his letter to Leopold of 16 Jan 1782:

Nun vom Clementi. — dieser ist ein braver Cembalist. — dann ist auch alles gesagt. — er hat sehr viele fertigkeit in der rechten hand. — seine haupt Pasagen sind die Terzen. — übrigens hat er um keinen kreutzer geschmack noch empfindung. — ein blosser Mechanicus.

der kayser that |: nach dem wir uns genug Complimenten machten :| den ausspruch, daß Er zu spiellen anfangen sollte. La santa chiesa Catholica sagte er. weil Clementi ein Römer ist. — er præludirte, und spiellte eine Sonate — dann sagte der kayser zu mir allons drauf los. — ich præludirte auch und spiellte variazionen. — dann gab die Grosfürstin Sonaten von Paesello her |: Miserable von seiner hand geschrieben :| daraus musste ich die allegro und er die Andante und Rondò spiellen. — dann nammen wir ein thema daraus, und führten es auf 2 Piano forte aus. — Merkwürdig ist dabey, daß ich für mich das Piano forte der gräfin thun gelehnt, und aber nur |: als ich allein gespiellt :| darauf gespiellt habe. — weil es der kayser also gewollt. — und Nb: das andere war verstimmt und 3 Tasten blieben stecken. — es thut nichts, sagte der kayser; — ich nemme es so, und zwar auf der besten Seite, daß der kayser Meine kunst und die Wissenschaft in der Musick schon kennt, und nur den fremden recht hat verkosten wollen. —

übrigens weis ich von sehr guter hand, daß er recht zufrieden war. der kayser war sehr gnädig gegen mich, und hat vieles heimlich mit mir gesprochen. — hat auch von meiner heyrath mit mir gesprochen. — wer weis — vielleicht — was glauben sie? — versuchen kann man es immer. — [Briefe, iii:192–93]

[translation:]

Now about Clementi. — He is a good cembalist. — And that says it all. He has very great facility with the right hand. — His main passages are thirds. — Apart from that, he hasn’t a kreuzer’s worth of taste or sensibility. — A mere technician.

The emperor (after we had complimented each other sufficiently) proclaimed that He should play first. La santa chiesa Catholica he said, because Clementi is a Roman. — He preluded and played a sonata — then the emperor said to me allons, go to it. — I preluded and played variations. — Then the Grand Princess gave us sonatas by Paisiello (miserably written in his hand); I had to play the Allegros and he the Andantes and Rondòs. — Then we took a theme from these and worked it out on two pianofortes. — An odd thing is that I had borrowed Countess Thun’s pianoforte for myself, but only played on it when I played alone. — Because that’s what the emperor wanted. — and NB: the other was out of tune and had three stuck keys. — It doesn’t matter, the emperor said; — and I took it as it was, and made the best of it, because the emperor already knows my art and knowledge in music and only wanted to sample the foreigner.

I also have it on good authority that he was quite pleased. The emperor was very gracious to me, and said much to me privately. — He also talked to me about my marriage. — Who knows — perhaps — what do you think? — One can only try. —

This passage was first published in Nissen’s Mozart biography in 1828 (Nissen 1828, 449). Mozart probably meant “Cembalist” as an insult. It can be translated (in the context of that time) as “keyboardist,” but by that time Mozart probably understood it to mean “harpsichordist,” or perhaps “Italian keyboardist.” (It was probably still the Italian word that Clementi used to describe himself.) At any rate Mozart surely did not mean it as a compliment.

Mozart refers to Clementi a few more times in later letters, most notoriously in a letter to Leopold of 7 Jun 1783 in which he addresses his comments about Clementi to Nannerl:

— Nun muß ich meiner schwester wegen den clementischen Sonaten ein paar worte sagen; — daß die komposizion davon nichts heisst, wird Jeder der sie spiellt, oder hört, selbst empfinden; — Merkwürdige oder auffallende Pasagen sind keine darin ausgenommen die 6:ten und 8:ven — und mit diesen bitte ich meine schwester sich nicht gar zu viel abzugeben, damit sie sich dadurch ihre ruhige, statte hand nicht verdirbt, und die hand ihre natürliche leichtigkeit, gelengigkeit, und fliessende geschwindigkeit dadurch nicht verliert. — denn was hat man am Ende davon? — sie soll die 6:ten und 8:ven in der grösten geschwindigkeit machen, |: welches kein Mensch wird zuwegen bringen, selbst clementi nicht :| so wird sie ein entsezliches Hackwerk hervorbringen, aber sonst weiter in der Welt nichts! — Clementi ist ein Ciarlattano wie alle Wälsche. — er schreibt auf eine Sonata Presto auch wohl Prestißimo und alla Breve. — und spiellt sie Allegro im 4/4 tackt; — ich weis es, denn ich habe ihm gehört. — was er recht gut macht sind seine 3:ten Paßagen; — er hat aber in London Tag und Nacht darüber geschwizt; — ausser diesem hat er aber nichts — gar nichts — nicht den geringsten vortrag, noch geschmack, — viel weniger Empfindung. — [Briefe, iii:272]

— Now I must say a couple of words to my sister about Clementi’s sonatas; — that the compositions amount to nothing will be felt by everyone who plays or hears them; — Noteworthy or striking passages there are none, apart from the sixths and octaves. — And I ask my sister not to bother about these too much, so that she does not spoil her calm and even hand, and does not lose her natural lightness, suppleness, and fluent velocity. — For what is the point of this? — she is supposed to play the sixths and octaves with the greatest velocity (which no person can accomplish, not even Clementi), whereby she produces only a terrible mishmash, but absolutely nothing else! — Clementi is a ciarlatano, like all Italians. — He writes presto on a sonata, or even prestissimo and alla breve — and plays it allegro in 4/4 time; — I know it, because I have heard him. — What he does quite well are his passages in thirds; — but he sweated day and night over these in London; — and apart from this he has nothing — nothing at all — not the least execution nor taste — much less sensibility.

Mozart’s assessment of Clementi is perhaps more scathing than his assessment of any other keyboardist or composer, and he keeps returning to his negative opinion like an itchy scab. His judgment on Clementi’s lack of artistry may have been well founded (as we shall see, Clementi later admitted this was so), but the sharpness with which Mozart expresses it suggests someone not accustomed to having his predominance on the keyboard challenged, who may have been rattled by encountering a performer who could do at least one thing better than he could.

Count Zinzendorf notes in his diary on 5 Dec 1782 that the emperor was talking about the Mozart-Clementi contest nearly a year later:

[...] J’y restois jusques vers 9^h. n’ayant pû partir a cause de l’arrivée de l’Empereur, qui parla infiniment musique, du combat entre Mozhardt et Clementi.
[Dokumente, 184; Addenda, 40]

I remained [at Countess Pergen’s] until around 9 pm, not being able to leave because of the arrival of the emperor, who talked incessantly about music, the battle between Mozart and Clementi.

As we show in our addendum on Zinzendorf’s entry, the emperor was probably describing the contest to Zinzendorf’s visiting cousin Baroness Louise Diede zum Fürstenstein,whom the emperor had just met. She was herself a fine keyboard player: Zinzendorf heard her play music by Mozart at Countess Oeynhausen’s the following day, 6 Dec 1782.

In his autobiography, published in 1801, Dittersdorf reports a conversation with the emperor about Mozart and Clementi:

[...]
     Kaiser. [...] Haben Sie den Mozart spielen gehört?

     Ich. Schon dreymal.

     Kaiser. Wie gefällt er Ihnen?

     Ich. So wie er jedem Kenner gefallen muß.

     Kaiser. Haben Sie auch den Clementi gehört?

     Ich. Ich habe ihn auch gehört.

     Kaiser. Einige ziehen ihn dem Mozart vor, worunter Greybig à la Tête ist. Was ist 
Ihre Meynung hinüber? Gerade heraus!

     Ich. In Clementi’s Spiel herrscht blos Kunst, in Mozarts aber Kunst und 
Geschmack.

     Kaiser. Eben das habe ich auch gesagt. Ist es doch gerade, als wenn wir beyde
aus einerley Buch studirt hätten.

     Ich. Das haben wir auch und zwar, aus jenem großen Buche Erfahrung.

     Kaiser. Was sagen Sie zu Mozarts Komposition? [...]
     [Dittersdorf 1801, 236–37]

[translation:]

[...]
     Emperor: [...] Have you heard Mozart play?

     Me: Already three times.

     Emperor: How do you like him?

     Me: Just as every connoisseur must.

     Emperor: Have you heard Clementi?

     Me: I have also heard him.

     Emperor: Some prefer him to Mozart, among whom Kreybig is at the head. What is 
your opinion? Out with it!

     Me: In Clementi’s playing there is merely art, but in Mozart’s there is art and taste.

     Emperor: That is just what I have said too. It is exactly as if the two of us had studied from the same book.

     Me: And so indeed we have, from that great book of experience.

     Emperor: What do you say about Mozart’s compositions? [...]

This conversation tells us nothing about the actual contest, but it suggests that the emperor was still fixated on it some years later: this conversation would most likely have taken place in 1785 or 1786, when Dittersdorf was visiting Vienna. As Unger has pointed out, however, Dittersdorf could only have heard Clementi during the latter’s sojourn in Vienna at the end of 1781 and the beginning of 1782 (Unger 1913, 32), a point to which we shall return.

The earliest known published reference to the contest is Clementi’s inscription on Breitkopf & Härtel’s 1804 edition of a revised version of his Sonata in B-flat, op. 24/2:

Cette Sonate, avec la Toccata, qui la suit, a été jouée par l’auteur devant S. M. I. Joseph II. en 1781; Mozart étant présent.

This sonata, with the toccata that follows it, was played by the author before His Imperial Majesty Joseph II in 1781, Mozart being present.

(The inscription also appears on Tranquillo Mollo’s edition of op. 24/2 that same year, but without the reference to the toccata.) The earliest substantive references to the contest in print are two anecdotes of unknown provenance; both may ultimately derive from credible sources, but both give the impression of having been embroidered and modified in the retelling. The first appeared in the Berliner Spenersche Zeitung on 7 Feb 1805 (see Unger 1913, 26n2), and was reprinted in the Wiener allgemeine musikalische Zeitung on 1 Dec 1813:

⁣    Ein berühmter Tonkünstler war von dem Kaiser
Joseph II. nach Wien berufen worden, und wurde,
wenige Stunden nach seiner Ankunft, zu einem Konzerte
nach Hofe bestellt.
    Er trat in den Konzertsaal, und fand ihn noch
leer. Bald darauf trat ein Mann herein, grüßte ihn
kalt, und stellte sich an den Ofen, ohne ihn anzureden.
    Aus langer Weile setzte sich jener an ein Forte=
piano, und phantasirte.
    Nach einer Weile setzte sich der andere auch an ein
Instrument, und führte jedesmal, wenn jener mit einem
Thema fertig war, ein ähnliches aus.
    So unterhielten sie sich, so machten sie ihre gegen=
seitige Bekanntschaft, ohne ein Wort zu wechseln.
    Doch endlich, bei einer vorzüglich schönen Stelle
fuhr der Fremde auf:
    “Sie sind Mozart!”
    “Sie sind Clementi!” antwortete der andere,
und sie fielen sich in die Arme.
[Wiener allgemeine musikalische Zeitung, No. 46,
Wed, 1 Dec 1813, col. 718]

[translation:]

⁣    A famous musician was summoned to Vienna by
Emperor Joseph II, and a few hours after his arrival
was ordered to come to a concert at court.
    He entered the concert hall and found it still
empty. Soon afterwards a man entered, greeted him
coldly, and placed himself next to the heating oven,
without speaking to him
    Out of boredom the former sat down at a fortepiano
and improvised.
    After a while the other also sat down at an instrument,
and each time that the first finished with a theme, the
other played a similar one.
    Thus they entertained themselves, and became
acquainted with one another without exchanging a word.
    But finally, after an exquisitely beautiful passage, the
foreigner exclaimed:
   “You are Mozart!”
   “You are Clementi!” answered the other,
and they fell into one another’s arms.

A charming story, resonating to some degree with Clementi’s own account of his encounter with Mozart, as reported by his former student Ludwig Berger in 1829 (see below), but probably best seen as a good yarn that embellishes an actual event, rather than a reliable report.

Three issues later, the Wiener allgemeine musikalische Zeitung published another anecdote about the contest:

⁣    Clementi, der größte Klavierspieler Italiens,
gleich stark im Vortrage des Adagio und Allegro, wurde
nebst Mozart von dem Kaiser Joseph II., als ihn
Leopold besuchte, eingeladen, jeder seine Symphonie
zu spielen.
    Beide spielten sie brav. Darauf wurden die Noten
gewechselt; Clementi exekutirte Mozarts Stück
wacker. Mozart fing Clementis Stück, das in
E gesetzt war, aus H an zu spielen. Clementi meinte
es sey ein Mißgriff, und zitterte für ihn und sein
Stück.
    Aber Mozart setzte es sogleich im Kopfe um, und
spielte es ohne Anstoß bis zum Ende durch.
    Da gestand Clementi, daß Mozart sein Sie=
ger sey, und den Vorzug vor ihm verdiene.
[Wiener allgemeine musikalische Zeitung, No. 49,
Sat, 8 Dec 1813, col. 766]

[translation:]

⁣    Clementi, Italy’s greatest keyboard player,
equally strong in the performance of Adagios and
Allegros, was invited, along with Mozart, by Emperor
Joseph II when Leopold was visiting him, each to
play his symphony.
    Both played well. Then the music was exchanged.
Clementi played Mozart’s piece valiantly. Mozart
began to play Clementi’s piece, which was in E, in
the key of B. Clementi thought it was a mistake, and
feared for him and his piece.
    But Mozart had transposed it instantly in his head,
and played it without problem through to the end.
    Then Clementi admitted that Mozart was
the victor, and had earned preference over him.

Again a charming story, but at considerable variance with more credible sources. The reference to Clementi and Mozart playing one another’s “symphonies” is odd, particularly for a music magazine. It was not Archduke Leopold, Joseph’s brother, who was visiting Vienna at the time of the contest, but Grand Duke Paul of Russia and his wife. (Leopold was Grand Duke of Tuscany, which may account for the confusion.) It is entirely plausible that Mozart could have transposed a piece from E to B at sight—but we have it on Clementi’s own authority that he performed his Sonata in B-flat, op. 24/2, so the key given in the anecdote is wrong.

The first published account from a credible source is a brief paragraph in the biography printed in The Quarterly Musical Magazine and Review in 1820, probably based on information provided by Clementi himself.

At Vienna he [Clementi] became acquainted with HAYDN, MOZART, and all the celebrated musicians resident in that capital. The Emperor Joseph II. who was a great lover of music, invited him to his palace, where, in the latter end of the year 1781, he had the honour of playing alternately with MOZART before the Emperor, and the Grand Duke Paul of Russia and his Duchess. [The Quarterly Magazine and Review, 1820, ii:311]

This tells us nothing about the encounter except that it took place, that they played alternately, and that both the grand duke and duchess were present (Mozart does not mention the grand duke). It is therefore Bridi’s anecdote in 1827 that provides the first detailed account of the event from a potentially credible source to appear in print, and for that reason we need to take it seriously, particularly given that Bridi lived in Vienna in the 1780s and knew Mozart, and his anecdote does not appear to be derived from any other source.

The passages from Mozart’s letters about the contest did not appear in print until 1828, in Nissen’s biography. In 1829, evidently in response to Mozart’s negative statements about Clementi printed there, Clementi’s own first-hand account of the contest was reported in Cäcilia by his former student Ludwig Berger. Berger places his conversation with Clementi in 1806, before the duel had been described in any published source (apart from the anecdote of unknown provenance published in Berlin the previous year).

[238]
⁣                          Erläuterung
               eines Mozartschen Urtheils
                                über
                      Muzio Clementi.

Die, unlängst bei Breitkopf und Härtel erschienene,
Biographie Mozarts, enthält, pag. 449, in einem
seiner darin aufgenommenen Briefe, Aeusserungen
und Kunsturtheile über Muzio Clementi, die
billig eine erläuternde Anmerkung der Herausgeber
verdient und auch gefunden haben möchten, könnte
man annehmen, dass ihnen die Kunstentwicke-
lungs-Epochen Clementi’s genauer bekannt
waren.
    Da jene Biographie gewiss ein fernhin dauerndes
Interesse und so manche Leser haben wird, die, über
musikalische Gegenstände weniger unterrichtet, Cle-
menti nur dem Namen nach kennen, und die deshalb
Mozarts hartes Urtheil bei vorkommenden Fällen zur
Basis ihrer Ansichten und Urtheile über Clementi
nehmen dürften, so fordert schon die allgemeine Bil-
ligkeit jedes näher Unterrichteten, wie viel mehr also
Pflicht und Anhänglichkeit eines ehemaligen Schüler’s
Clementi’s, wie der Unterzeichnete sich nennen kann,
einige Berichtigungen hierüber den theilnehmenden
Kunstfreunden mitzutheilen.
    Ich glaube meinen Zweck zunächst zu erreichen,
wenn ich, über die im Jahre 1781 vor dem Kaiser
Joseph II. statt gehabte Concurrenz der beiden Künst-
ler, Clementi’s eigene Aeusserungen, so viel ich mich
deren erinnere, hier einfach wiedergebe:
    »Kaum einige Tage in Wien anwesend, erhielt
»ich von Seiten des Kaisers eine Einladung, mich
»vor ihm auf dem Fortepiano hören zu lassen.
    »In dessen Musiksaal eintretend, fand ich daselbst
»jemand, den ich, seines eleganten Aeussern wegen,

[239]

»für einen kaiserlichen Kammerherrn hielt; allein
»kaum hatten wir eine Unterhaltung angeknüpft, als
»diese sofort auf musikalische Gegenstände überging,
»und wir uns bald als Kunstgenossen — als Mozart
»und Clementi — erkannten und freundlichst be-
grüssten.« 
  Aus dem Fortgange der Erzählung Clementi’s
(ganz übereinstimmend mit der Mozartschen Angabe)
ging hervor, wie sehr ihn die Kunstleistungen des
Letztern ergriffen und entzückten.
    »Ich hatte bis dahin niemand so geist- und an-
»muthvoll vortragen gehört. Vorzugsweise über-
»raschten mich ein Adagio und mehrere seiner ex-
»temporirten Variationen, wozu der Kaiser das The-
»ma wählte, das wir, wechselseitig einander akkom-
»pagnirend, variiren mussten.
    Auf meine Frage, ob er damals schon in seinem
jetzigen Style (es war im Jahre 1806) das Instru-
ment behandelt hätte, verneinte er dies, hinzu-
setzend:
    »Dass er in jener früheren Zeit sich vorzugs-
»weise noch in grosser brillirender Fertigkeit und
»besonders in denen vor ihm nicht gebräuchlich ge-
»wesenen Doppelgriff-Passagen und extemporirten
»Ausführungen gefallen, und erst später den gesang-
»vollern, edlern Styl im Vortrage, durch aufmerk-
»sames Hören damaliger berühmter Sänger, dann
»auch durch die allmählige Vervollkommnung beson-
»ders der englischen Flügel-Fortepiano’s, deren
»frühere mangelhafte Construktion ein gesangvolle-
»res, gebundeneres Spiel fast gänzlich ausgeschlos-
»sen, sich angeeignet habe.«
    So, scheint mir, erklärt sich Mozarts Urtheil, das
Jenen als »geschmack- und empfindungs-
los« bezeichnet, und deshalb nur zu Missdeutungen
zum Nachtheile Mozart’s veranlassen dürfte, doch ei-
nigermassen — natürlich.

[...]

     Berlin, im Juni 1829.
                                                                              Ludwig Berger.

[Cäcilia, Jul 1829, x/40: 238–40; see also Dokumente, 464–65]

[translation:]

⁣                           Clarification
                   of Mozart’s Judgment
                                    of
                       Muzio Clementi.

The biography of Mozart recently published by
Breitkopf und Härtel contains, in one of his letters
included therein (p. 449), statements and artistic
judgments on Muzio Clementi that fairly deserve an
explanatory note from the publisher, and might have
found one, if it could be assumed that the stages of
Clementi’s artistic development had been more well
known to them.
    Because that biography will certainly be of lasting
interest and will have so many readers—who, less
educated in musical matters, will know Clementi only
by name, and because Mozart’s harsh judgment could
under the present circumstances become the basis
of their views and judgment of Clementi—ordinary
fairness demands that someone better informed—
who moreover has the duty and allegiance of a former
student of Clementi’s, as the undersigned can call
himself—communicate some corrections about this to
sympathetic lovers of the art.
    I believe I can first achieve my goal if I reproduce here
Clementi’s own statements about the competition of the
two artists before Emperor Joseph II in 1781:
    “Having been in Vienna only a few days, I received
from the emperor an invitation to play the fortepiano for
him.
    “Entering his music room, I found someone who,
from his elegant appearance, I took to be an imperial
chamberlain; but scarcely had we engaged in conversation
when it turned to musical matters and we recognised one
another as comrades in art—as Mozart and Clementi—
and greeted one another in the friendliest manner.”
    From the continuation of Clementi’s story (completely
in agreement with Mozart’s account), it becomes clear
how much the artistic accomplishments of the latter
moved and enchanted him.
    “Up to then I had heard no one perform so brilliantly
and beautifully. I was particularly surprised by an Adagio
and several of his improvised variations, for which the
Emperor had provided the theme, which we had
to vary in alternation while the other accompanied.” 
  To my question, whether he had handled the instrument
at that time in his current style (this was in 1806), he said
that he had not, adding:
    “That in that earlier time he was particularly still caught
up ingrand and brilliant dexterity, and especially in
double-note passages, which had not been common
before him, and in improvised flourishes, and only later
adopted the more singing, noble style of execution,
through attentive listening to famous singers of the time
and then also through the gradual perfection of the English
grand fortepiano, whose earlier deficient construction
almost entirely precluded song-like, legato playing.”
   This, it seems to me, explains Mozart’s judgment,
denoting the former as “tasteless and without sensibility”,
thus risking misinterpretations to Mozart’s disadvantage,
and yet is to some degree, natural.
[...]
     Berlin, June 1829.
                                                                              Ludwig Berger.

Clementi gives relatively little detail about the actual contest with Mozart, but he does imply that neither had been expecting to meet the other. His account agrees with Mozart’s in saying that they alternately varied a theme on two pianos.

A biography of Clementi published in The Harmonicon in 1831 is derived from the one in The Quarterly Musical Magazine and Review in 1820, but includes a greatly expanded account of the duel. This new account seems to reflect acquaintance with Mozart’s own description, as published in Nissen’s biography, but with differences in detail that could possibly stem from Clementi, who was still alive (he died in 1832):

⁣                                                       In Vienna he [Clementi]
became acquainted with Haydn, Mozart, Salieri, and
many other celebrated musicians then resident in that city;
and played alternately with Mozart, before the Emperor
Joseph II. and the Grand Duke (afterwards Emperor)
Paul of Russia and his consort. On one occasion, when
the imperial trio alone were present, Clementi and Mozart
were desired to play; some question of etiquette arising
as to who should make the first display of his powers, the
emperor decided it by motioning Clementi to his instru-
ment, saying at the same time, in allusion to his Roman
birth, “tocca all eglese di dar l’essempio [sic].” Clementi hav-
ing preluded for some time, played a sonata, followed by
Mozart, who, without any further exordium than striking
the chord of the key, also performed a sonata. The Grand
Duchess then said, that one of her masters had written
some pieces for her which were beyond her powers, but
she should very much like to hear their effect; and, pro-
ducing two, Clementi immediately played one, and Mozart
the other, at sight. She next proposed a theme, on which,
at her request, these two great masters extemporized alter-
nately, to the astonishment, as well as delight, of their
imperial audience. The plan was evidently premeditated,
and hardly fair towards the eminent professors, who were
thus surprised into an immediate competition and compa-
rison of abilities. The result was equally honourable to
them as men, between whom there was no unworthy feel-
ing of jealousy, and creditable to them as artists, on whose
talents no demand, however unexpected or unusual, could
be too great.
[The Harmonicon, 1831, 184]

The outline of the event as described here matches Mozart’s account, but several differences in detail suggest that information may have been added from another source, perhaps Clementi. The Harmonicon states that the grand duke was present, whereas Mozart does not mention him. Mozart writes that he “preluded” (“ich præludirte”), whereas The Harmonicon says that he simply played a chord before launching into a “sonata.” Mozart, on the other hand, writes that he played variations. Mozart does not specify who provided the theme that he and Clementi varied on two pianos, but The Harmonicon has the grand duchess providing it. The Harmonicon states that they played “pieces” (not “sonatas,” as Mozart writes) by her keyboard teacher (who was, in fact, Paisiello).

The most striking difference between the accounts is what the emperor is quoted as saying. Mozart has him saying “La santa chiesa Catholica” (“The holy Catholic church”), whereas The Harmonicon has “tocca all eglese di dar l’essempio.” Given that the author of this passage in The Harmonicon almost certainly knew Mozart’s account from Nissen’s biography and could simply have copied Mozart, the change seems to have been intentional. The most plausible motivation for the change is Clementi himself. In fact, “eglese” is not an Italian word and “esempio” is properly spelled with one ‘s’ not two. The phrase could thus perhaps have been intended to show Joseph’s less than perfect command of Italian, a language he probably used much less often than French. Thus Joseph might well mistakenly have used an italianized version of the French “église” for “church” (instead of recalling the correct “chiesa”), and “essempio” might be intended to mimic Joseph’s pronunciation of that word with an unvoiced /s/ rather than the standard voiced /z/. (A lack of consonant voicing is common in Viennese German.) One can imagine that Mozart, in reporting the event to his father, would not have wanted to make fun of Joseph’s Italian, given that he was trying to emphasize his own promising prospects at court. The Harmonicon’s “tocca all eglese di dar l’essempio” can be translated as “let the church go first to set the example.” Bridi differs from these accounts in saying that it was the grand duchess who summoned Clementi to begin.

Thus we have four accounts of the duel stemming directly or indirectly from potentially reliable (but by no means disinterested) witnesses: Mozart’s own account, in his letter to Leopold of 16 Jan 1782 (not published until 1828); Clementi’s brief account as reported by Berger in 1829; the description in The Harmonicon in 1831, which could be based in part on information from Clementi, but also suggests acquaintance with Mozart’s version in Nissen’s biography; and Bridi’s anecdote from 1827, the earliest of the four by date of publication, and apparently independent of the other three.

Bridi came to Vienna in the 1780s, initially to further his education in business. We do not know precisely when he arrived, but we cannot rule out the possibility that he was already in Vienna in 1781 (he would have been eighteen at the time). However, he almost certainly did not witness the duel first hand: by all accounts it was a private event at court. All sources agree that the emperor and grand duchess were present, as were of course Clementi and Mozart. The Quarterly Musical Magazine and Review and The Harmonicon claim that the grand duke also attended. It seems likely that there would also have been at least a few retainers present “anonymously” (as retainers often were), or waiting just outside. But Bridi was very well placed to hear reliable second-hand accounts of the duel: he certainly knew Mozart by no later than Mar 1786, the time of the production of Idomeneo at Prince Auersperg’s, and he may well have met him even earlier; and Mozart refers to Bridi in a letter to Gottfried von Jacquin on 4 Nov 1787 as a “good friend” (Briefe, iv:58; see our entry “Paisiello and Idomeneo”). Bridi, by all accounts an outstanding amateur tenor, remained deeply involved in Viennese musical life until his eventual retirement to his estate in Rovereto, probably in the 1820s. Given that Bridi’s anecdote may derive from sources close to the event (perhaps even Mozart himself), it may be enlightening to compare his account point by point with the other three. None addresses every aspect of the event, so any reconstruction must be stitched together from all four.

• Clementi (as quoted by Berger) says only that Mozart played variations, and that he and Mozart alternated playing variations and accompanying. Clementi states that the emperor provided the theme for the latter, whereas The Harmonicon claims that the theme was provided by the grand duchess. Mozart does not specify who selected it, but writes that it came from one of the Paisiello “sonatas” that he and Clementi had just sight-read from messy autographs. Bridi’s anecdote ends with Mozart’s improvising solo variations based on a theme from Clementi’s sonata, and the grand duchess conceding defeat in the wager. Bridi does not mention Clementi and Mozart sight-reading pieces by Paisiello or trading variations on two pianos.
  
• Clementi (as reported by Berger) makes clear that he had not known ahead of time that he would be competing against Mozart, and his letter to his father on 24 Dec 1781 is consistent with this, saying only that he has been summoned to play for the grand duchess, with no mention of Mozart or a competition. Mozart does not say whether he knew ahead of time of the contest. Bridi’s anecdote strongly implies that neither of them knew.
  
• Bridi is the only source to mention a wager, and the only one to state that the grand duchess championed Clementi and the emperor Mozart. However, Mozart’s statement that the emperor was pleased, and Dittersdorf’s later reported conversation with the emperor are both consistent with the notion that Joseph was the advocate for the recently arrived star from Salzburg.
  
• In Bridi’s description, each musician waits in a separate room while the other plays. The other three accounts do not address this point directly, although all four are consistent with the idea that Mozart and Clementi met one another before beginning to play and could hear each other during the solo performances. This last does not necessarily contradict Bridi’s account: in 18th-century palaces, an antechamber might well open directly into a larger adjoining room, and Bridi makes clear in any case that Mozart could hear Clementi’s solo performance.
  
• Mozart, Bridi, and The Harmonicon agree that Clementi played first and performed a sonata (his Sonata in B-flat, op. 24/2, according to the annotation on the Breitkopf and Mollo editions of that work in 1804).
  
• Mozart, Bridi, and Berger’s Clementi agree that Mozart played solo variations. Alone among the sources, Bridi says that the emperor told Mozart “di mettersi al forte-piano e di sonare a sua fantasìa ciò, che più gli fosse piaciuto” (“ to sit at the fortepiano and to improvise whatever he pleased”). Although this is not directly substantiated in any other source, it is entirely plausible, as by that point Mozart’s improvisational abilities were well known to the emperor and the Viennese public, and the emperor might thus have been disposed to show them off to his distinguished visitors. The Harmonicon, on the other hand, states that Mozart played a sonata, which is consistent with the anecdote of unknown provenance in the Wiener allgemeine musikalische Zeitung on 8 Dec 1813 that Mozart played Clementi’s sonata, but in a different key. But that anecdote could be a garbled word-of-mouth echo of Mozart improvising variations on a theme from Clementi’s sonata, as Bridi claims. Mozart and The Harmonicon (the latter perhaps drawing on Mozart’s letter as printed in Nissen) agree that both musicians sight-read pieces by Paisiello from autographs, and both agree (as does Berger’s Clementi) that they ended by playing on two pianos, alternately varying and accompanying a selected theme. Mozart (but none of the other sources) states that the theme came from one of the pieces by Paisiello that they had just played. 

In his letter to Leopold on 16 Jan 1782, Mozart writes:

dann gab die Grosfürstin Sonaten von Paesello her |: Miserable von seiner hand geschrieben :| daraus musste ich die allegro und er die Andante und Rondò spiellen.

Then the Grand Princess gave us sonatas by Paisiello (miserably written in his hand); I had to play the Allegros and he the Andantes and Rondòs.

To a modern reader, this implies that Clementi and Mozart were asked to sight-read three-movement keyboard sonatas following the typical late eighteenth-century sequence fast-slow-fast, with the last movement a rondeau. There is, however, a problem: Paisiello is not known to have written any keyboard sonatas of this sort (on this point, see Robinson 1991, 202). What, then, did they play?

Paisiello spent the years 1776 to 1784 in St. Petersburg in the service of the Russian Empress Catherine the Great. It is the only period of Paisiello’s life during which he did any substantial keyboard teaching, and most of his authenticated keyboard works were composed during his time in Russia. (The exceptions are six keyboard concertos composed later in the 1780s for the Infanta Maria Luisa of Spain; on Paisiello’s keyboard works, see principally Hunt 1975.) Paisiello’s keyboard works from his years in Russia include two concertos and a collection of miscellaneous items for solo keyboard. The autograph score of the Keyboard Concerto in F (R. 8.11) carries a dedication to the grand duchess. The autographs of the miscellaneous items are lost, but the canonical source is taken to be a manuscript copy dated 1783 from the private music collection of Empress Marie Therese (Maria Teresa, daughter of King Ferdinand IV of Naples, and later the second wife of Emperor Franz II/I). That copy, now in the Austrian National Library (ÖNB, Mus. Hs. 12742), is thought to be the one that Paisiello had made for her in 1783 (Hunt 1975, 217). The manuscript as currently bound contains two volumes; the first title page reads:

Paisiello, in a letter dated 8 Sep 1781 to his friend Ferdinando Galiani in Naples, refers to his keyboard student the grand duchess:

Non voglio mancare però di dirle che S. A. I. la Gran Duchessa mi fa molto onore per il progresso che ha fatto nella musica per il tempo che ho avuto l’onore di darle lezione. Mi ha data parola di esercitarsi quando potrà nel tempo del suo viaggio, onde spero che la farà.
[Hunt 1975, 214n3, citing Salvatore Panareo, Paisiello in Russia (Trani, 1910), 28]

I don’t want to fail to tell you that Her Imperial Highness the Grand Duchess does me great honor by the progress she has made while I have had the honor of giving her lessons. She has promised to practice whenever she can while she is on her trip, and I hope she does.
[translation: Hunt 1975, 214]

By Paisiello’s own account, the grand duchess promised that she would practice whenever possible during her European tour with her husband, so she will undoubtedly have brought music along with her on the tour.

Michael Robinson plausibly suggests that the pieces Clementi and Mozart were asked to sight-read on 24 Dec 1781 would have come from the pieces in Mus. Hs. 12742 (Robinson 1991, 202). The “1783” on the main title page should be seen as the date when the copy was made, not the date of composition. It seems safe to assume, at any rate, that the grand duchess had with her autographs (now lost) of at least some of these pieces.

Mus. Hs. 12742 does not contain any sonatas with three movements, although it does contain a sonata with two. The first volume begins with six pairs of preludes and rondos (to use the collection’s most frequent spelling of the latter word). The preludes are all quite brief and without indications of tempos, and the rondos are all in moderate tempos and technically rather easy, befitting an amateur pupil at an intermediate level. These pairs are followed by a keyboard reduction of the overture to Paisiello’s Alcide al bivio (St. Petersburg, 1780), one of the very few actual Allegros in the collection. The overture is followed by six more “Rondos,” then a keyboard reduction of the chorus “Vergine bella e pura” from Paisiello’s Nitteti (St. Petersburg, 1777). The volume ends with a “capriccio.” If any of the rondos were among the movements that Clementi or Mozart had to read at sight, they would probably have found them quite easy, even allowing for Paisiello’s alleged sloppy handwriting. The only Allegro in the volume, the overture, is also relatively easy.

The content of the second volume of the grand duchess’s collection is more various. It opens with the only three-movement item in the collection: a keyboard reduction of the overture to Nitteti. The movements are: Allegro, D major–Andante, G major–Allegro, D major. This is the only candidate for an integral three-movement “sonata” in the collection, and again, the level of difficulty is only moderate.

The rest of the second volume is a hodge-podge: nine more “rondos,” two “capriccios,” a “notturno,” and a “canzone,” intermixed with keyboard arrangements of a chorus from Achille in Sciro (St. Petersburg, 1778), the overture of Il barbiere di Siviglia (St. Petersburg, 1782, thus dating from after the Mozart-Clementi duel), a chorus from Il gran Cid (Florence, 1775), and the overture from La passione di nostro Signor Gesù Cristo (also composed later than the duel). The volume ends with a pair of movements: a Largo and a “Rondeaux” Andante. The first carries the heading “Sonata a Cembalo Solo”—the only occurrence of this title in Paisiello’s authenticated works for keyboard. This “sonata” could account for one pair of movements played by Clementi as per Mozart’s description, but (so far as we know) it lacks a corresponding opening Allegro that Mozart might have performed.

The second capriccio in Mus. Hs. 12742, in D minor, survives in copies titled “Les Adieux de la grande Duchesse des Russies” or some variant of this, suggesting a piece written for the departure of the grand duchess on her European tour with her husband. The title of the canzone, “La partenza” (also in D minor) suggests a similar connection.

In the absence of additional information, we cannot know for certain what pieces Mozart and Clementi were asked to sight-read on 24 Dec 1781, but the collection dedicated to the grand duchess includes items that offer a few plausible (if not exact) fits with the documentary evidence. It is even conceivable that the odd reference to “symphonies” in the anecdote published in the Wiener allgemeine musikalische Zeitung on 8 Dec 1813 is a corrupted echo of a performance of the overture from Nitteti (marked “Sinfonia” in Mus. Hs. 12742). Whatever the case may be, none of the pieces in the grand duchess’s collection are likely to have caused problems for Clementi or Mozart, even allowing for messy handwriting, and thus the sight-reading may have been the least challenging part of the competition.

The only aspect of Bridi’s anecdote that seems inconsistent with what we know from other sources is his statement that Clementi “godeva in sommo grado la protezione della gran Principessa delle Russie” (“enjoyed to the highest degree the protection of the grand princess of the Russias”). In fact, it seems certain that the grand duchess would never previously have had the opportunity to hear Clementi, and Clementi’s own statement in his letter to his father on 24 Dec 1781 certainly implies this: “sta sera avrò l’onore d’essere introdotto alla Gran Duchessa che vuol sentirmi sul cembalo” (“this evening I shall have the honor to be introduced to the grand duchess, who wishes to hear me on the cembalo”). However, it is entirely possible that the grand duchess had heard high praise of Clementi from her network of noble relations and acquaintances, and this may have made her inclined to argue for Clementi’s superiority and to accept Joseph’s wager. The wager described by Bridi is not attested in any other known source, but neither do we have any reason to discount it.

The emperor’s evident fondness for promoting musical rivalries lends support to Bridi’s story. By inviting the prima donna Celeste Coltellini to join his opera buffa troupe in 1785, when Nancy Storace was at the height of her popularity in Vienna, the emperor certainly knew that he was making competition between the sopranos inevitable (Rice 1998, 339–40). Salieri brought the two sopranos together on the same stage in La grotta di Trofonio, in which they portrayed sisters with completely different personalities that are magically exchanged halfway through the opera. In 1786 Joseph organized a rivalry on an even grander scale, between his Italian and German opera companies, commissioning an Italian work from Salieri and Giovanni Casti (Prima la musica e poi le parole) and a German one from Mozart and Johann Gottlieb Stephanie (Der Schauspieldirektor). These two short works were staged in the Orangerie at Schönbrunn on 7 Feb 1786 in honor of the visit to Vienna of Prince Albert von Sachsen-Teschen and his wife (Joseph’s sister) Archduchess Maria Christina. Thus there were rivalries on multiple levels: between the companies, between the composers and librettists, and once again between Storace and Coltellini. In Prima la musica, the two portray rival singers—a seria star (Storace) and a prima buffa (Coltellini)—forced to appear together in the same opera (see Rice 1998, 376–77).

The principal novelties of Bridi’s anecdote are the story of the wager, his emphasis on Joseph’s advocacy for Mozart, and the statement that in his solo performance, Mozart extemporaneously varied a theme from Clementi’s sonata. We know from the inscription on the 1804 editions of Clementi’s op. 24/2 (an inscription probably stemming from Clementi himself) that he played this sonata at the contest in 1781, along with his Toccata in B-flat, op. 11. No other source mentions the toccata, but it contains passages in thirds of just the kind that Mozart mentions (no such passages appear in the sonata). So there is no reason to doubt that Clementi played the sonata and the toccata on 24 Dec 1781.

The resemblance between the theme of the opening allegro of Clementi’s op. 24/2 and the overture to Die Zauberflöte was already pointed out by Berger (1829, 240), and has since become a staple of the literature on the two composers.

It is attractive to think that this might have been the theme that Mozart varied extemporaneously in the duel, calling to mind the scene in the film Amadeus in which Mozart spontaneously transforms Salieri’s march into “Non più andrai” during an audience with the emperor—with Salieri looking on in seething humiliation. But in the absence of corroborative evidence, the identity of the theme that Mozart varied on 24 Dec 1781 remains speculative.

Having made a critical examination of all credible sources, we are now in a position to give a new summary of the encounter between Mozart and Clementi, synthesizing the elements that seem most reliably attested:

Emperor Joseph II and the visiting Grand Duchess Maria Fyodorovna may have agreed to wager on a keyboard competition between Mozart, whose playing had taken Vienna by storm since he came to the city in Mar 1781, and the recently arrived Clementi, whose reputation as a virtuoso pianist probably preceded him via reports from London, Paris, and elsewhere. It seems likely that both musicians were summoned to court on 24 Dec 1781 without knowing in advance that the other had been summoned or that they would be pitted against one another. At (probably) Joseph’s command, Clementi went first, preluding, and then playing his Sonata in B-flat, op. 24/2 and his Toccata in B-flat. Then it was Mozart’s turn: after preluding, he extemporized variations, perhaps on a theme from Clementi’s sonata. The two were then given autographs by Paisiello to sight-read (probably not all literally “sonatas,” as Mozart writes), after which they played variations on two pianos, perhaps on a theme selected by the grand duchess or the emperor from one of the pieces by Paisiello. According to Bridi, the grand duchess immediately conceded defeat in the wager after hearing Mozart play; Bridi’s anecdote does not describe any part of the competition after the initial solo playing.

Bridi writes that the wager was “100 zecchini” (often translated in English as “sequins”). The Venetian zecchino, a gold coin, was at that time accepted in Austria on par with a Kremnitz ducat (worth 4 fl 18 kr in 1781), because it consisted of an equivalent weight of gold; the wager would, however, certainly have been made in ducats. (In his memoirs, Da Ponte likewise uses “zecchini” to refer to ducats when writing about his years in Vienna.) The emperor’s wager would more likely have been made in “kaiserliche” (imperial”) rather than Kremnitz ducats, which were worth slightly less at that time (4 fl 16 kr). Although we have no evidence on the point, it seems plausible that Mozart’s reward of 50 ducats might have come from the wagered money, with Clementi perhaps receiving the other half.

By Clementi’s own account he arrived in Vienna around 19 Dec 1781, and according to Mozart’s letter to his father of 8 May 1782, Clementi was leaving “morgen” (tomorrow), thus 9 May (Briefe, iii:209). So far as we know, Clementi remained in Vienna for that entire period, thus nearly five months. Yet there is no known trace of him in any other Viennese documents from the time. He is not known to have given any public or private concerts apart from his contest with Mozart. What was he doing in Vienna all that time?
According to the biography of Clementi in The Quarterly Musical Magazine and Review in 1820, likely based on information provided by the composer himself, during his time in Vienna Clementi composed four sets of three piano sonatas: op. 7, op. 8, op. 9, and op. 10 (on Clementi’s compositions in Vienna, see Tyson 1966 and Tyson 1967). Op. 7 was first announced by Artaria in the Wiener Zeitung on 25 Sep 1782, around five months after Clementi left. The title page reads (in its uncorrected first state):

TROIS SONATES / Pour le Clavecin ou Pianoforte / Composées par / MUTIUS CLEMENTI / Oeuver VII. / Dédiées / A MADAME DE HESS, NÉE DE LEPORINI. / par / Ses trés humbles, et trés / obeissants Serviteurs / Artaria Compag / publiées, et se vendent a Vienne chez les sudits Artarias Comp. Prix f 2  [Tyson 1967, 43]

The dedication is to Theresia von Heß (1754–1798), wife of Franz Joseph von Heß, a governmental advisor for Lower Austria. The entry for her in Schönfeld’s Jahrbuch der Tonkunst von Wien und Prag (1796, 28–29) states that she was indeed a student of Clementi:

⁣          Heß, Frau von, Gemahlinn des Hrn.
Regierungsraths. Sie ist eine ausgezeichne=
te Klavierspielerinn, eine Scholarinn Cle=
mentis. Sie hat viel Geschmack für kern=
hafte und erhabene Komposizionen, liest be=
sonders gut, spielt mit Ausdruck, Delika=
tesse und Geschwindigkeit, und hat einem
meisterhaften Anschlag. Nur Schade, daß
diese unserer ersten Klavierspielerinnen eine,
so wenig Muße mehr für ihre Kunst hat.

⁣          Heß, Frau von, wife of the Herr
Regierungsrat. She is an excellent keyboard
player, a student of Clementi. She has a strong
taste for substantial and elevated compositions,
reads especially well, plays with expression,
delicacy, and rapidity, and has a masterly
touch. It is only a pity that she, one of our
leading keyboard players, presently has
so little time for her art.

Her lessons with Clementi can only have taken place during his stay in Vienna in 1781 and 1782. Theresia von Heß was one of the subscribers to Mozart’s series of private concerts in the Trattnerhof in Mar 1784 (Briefe, iii:305; Dokumente, 487).

Clementi’s three sonatas op. 8, also said to have been composed in Vienna, were published in Lyon at the end of 1782 by Castaud (Tyson 1967, 44). The three sonatas carry separate dedications. The first is dedicated to “Mlle. Nancy D’AUENBRUGGER,” probably Anna Maria Simphorosa (“Marianna”) Auenbrugger (1759–1782), daughter of the famous doctor Leopold Auenbrugger in Vienna. Clementi, who was in France by that point, may not have known that she had died on 25 Aug 1782, before the publication of the sonata. Her older sister Maria Catharina (1756–1825), sometimes referred to as “Franziska,” was also a pianist of note. It seems likely that Marianna Auenbrugger and perhaps also her sister had been Clementi’s students.

Thus Clementi composed and taught piano while in Vienna. Mozart, in a letter to his father dated 23 Jan 1782, mentions that “Clementi auch eine Accademie geben wird” (“Clementi will also give an academy; Briefe, iii:294). We know, however, from Schletter’s comprehensive calendar of the court theaters for 1782 (Schletter 1783) that Clementi did not give a concert for his own benefit in either the Burgtheater or the Kärtnertortheater (Mozart gave a concert in the Burgtheater on 3 Mar 1782). Yet Dittersdorf tells Joseph (in the conversation quoted above) that he had heard Clementi, something that can only have happened when the latter was in Vienna between 19 Dec 1781 and 9 May 1782. It seems very unlikely that Dittersdorf would have witnessed the duel. It may be that Clementi appeared in private performances in Vienna about which we currently know nothing, and Dittersdorf might have heard Clementi at one of these. But perhaps Clementi participated in one or more public concerts given by other musicians.

Tyson points to a pair of canzonette for soprano and keyboard by Clementi (Tyson 1967, 100, WO 4), published by Artaria in 1792. An autograph survives in the library of Stanford University. According to Tyson, the first song (“Vieni oh caro amato bene”) bears the inscription “Rondeau per soprano e cembalo solo, fatto per il Cecarelli. Idea di Sacchini, variata da me Clementi” (Rondo for soprano and solo keyboard, written by Ceccarelli. Motive by Sacchini, varied by me, Clementi). The reference is to the castrato Francesco Ceccarelli (1752–1814), in the service of the Salzburg court from 1777 to 1788. The second song (“Senza il diletto mio”) is inscribed: “Andante con espressione di mè Ceccarelli” (Andante espressione, by me, Ceccarelli); Tyson suggests that the last three words were probably written by Ceccarelli himself. 

Clementi can only have encountered Ceccarelli in Vienna during his visit in 1781 and 1782, and we know from Mozart that Ceccarelli took part in a concert at court in Vienna on Christmas Day 1781, the day after Mozart’s contest with Clementi (Briefe, iii:188; see our entry for 8 Oct 1782). So it may be that the songs were composed for and performed at this concert, although Clementi, who had arrived in Vienna only six days earlier, would not have had long to write them. From Schletter (1783), we also know that Ceccarelli also gave a concert for his own benefit in the Burgtheater on Sun, 10 Mar 1782, a week after Mozart’s. Thus it is perhaps not too farfetched to suggest that these canzonette might have been written for and performed at Ceccarelli’s concert, with Clementi accompanying on piano. (The rondò has been published in a modern edition; see Clementi 1984. The opening text and melody are taken from an aria in Sacchini’s opera Il Cid, first performed in London in 1773.)

After spending time in Lyon and Zürich, Clementi finally returned to London by the fall of 1783 (Plantinga 1977, 69).

The contest between Mozart and Clementi had a lasting impact on both composers, and on Emperor Joseph, who had instigated it. Both Mozart and Joseph seem to have remained fixated on the event for some time afterward. For his part, Clementi’s published statements regarding Mozart are considerably more gracious than were Mozart’s private statements about Clementi. Clementi (according to Berger) praised Mozart’s playing very highly, with the implication that hearing Mozart helped motivate Clementi’s reassessment of his approach to the keyboard. The impact of Viennese composers on Clementi was already noted in the Magazin der Musik in 1787:

⁣     Nachrichten, Auszüge aus Briefen,
                      Todesfälle.
    1) Aus Italien, im Januar 1787.) [...]

    Vom Clementi ists gewiß, daß er bey seinem Auf=
enthalt in Wien von vielen deutschen Componisten,
hauptsächlich von Haydn, Mozart, Kozeluch gelernt
habe; denn von dieser Zeit an tragen seine neuesten
Werke deutschen Zuschnitt und richtigere Bearbeitung der
Mittelstimmen. Viel Genie wohnt in diesem Manne,
aber der Ausbildung davon hat er nicht den Italiänern
seinen Landsleuten, die ihn über alle jetzige Spieler und
Componisten setzen wollen, sondern den Deutschen zu
verdanken.
[Magazin der Musik, ii/2: 1378–79; see Neue Folge, 55]

⁣      News, Extracts from Letters,
                          Deaths.
    1) From Italy, January 1787. [...]

    Of Clementi, it is certain that he learned much from
German composers during his sojourn in Vienna,
particularly from Haydn, Mozart, and Kozeluch; for
after this time his most recent works show German
tailoring and a more correct working out of the
inner voices. Much genius lives in this man, the
cultivation of which he does not owe to the Italians—
his compatriots, who want to set him above all current
players and composers—but to the Germans.