Leopold Fischer (1703–1781) was a Jesuit preacher, librarian and historian. The first edition of his Brevis notitia urbis vindobonæ, a chronicle of Viennese history, appeared in 1764. An expanded edition appeared in four volumes and three supplements between 1767 and 1775; this item appears in the first supplement of 1771.
The “Chaosische Stiftung” was a foundation for the housing of orphans, funded from the testamentary legacy of Johann Konrad Richthausen, Freiherr von Chaos (1604–1663). A number of orphanages were built in Vienna in accordance with his wishes, and in 1767 the orphans moved to an expanded complex on the Rennweg which already housed another orphanage run by the Jesuit Ignaz Parhamer (1715–1786). Work began on a new chapel for the institution, and on 21 March 1768 Joseph II together with his sister Maria Carolina (1752–1814) laid the foundation stone for the chapel (Maria Carolina was soon to depart Vienna for Naples after her reluctant marriage by proxy to Ferdinand IV). On 7 Dec (not 7 Sep, as given by Fischer), the unfinished chapel was consecrated by Cardinal Migazzi, Archbishop of Vienna (1714–1803) with the suffragan Bishop Anton Marxer (1703–1775) presiding. Richthausen, whose legacy had funded the construction of the chapel, was reburied in its crypt.
According to Leopold Mozart, by 12 Nov Wolfgang had already written a solemn mass, an offertory and a trumpet concerto for this occasion (Briefe, i:285). The mass is probably the so-called Waisenhausmesse, K. 139, the offertory is possibly Benedictus sit deus, K. 117, but this attribution is problematic, and there is no trace of the trumpet concerto (K. 47c). Whatever the identity of the pieces, the occasion was a great success for Mozart (Dokumente, 78; see Black 2007 for the background to the event).