In late April 1791, Mozart wrote to the Vienna city council requesting an appointment as unpaid adjunct to Leopold Hofmann (1738–1793), Kapellmeister at St. Stephen’s Cathedral (Briefe, iv:131). Mozart is not known to have had any previous association with Hofmann, and the background to the request is unclear. The council was initially minded to reject Mozart’s request because Hofmann had not asked for an assistant. For reasons that are again unclear, this decision was reversed and Mozart was duly appointed on 9 May, with the understanding that he would succeed to the position on Hofmann’s resignation or death (Dokumente, 346).

The nature of Mozart’s duties in the seven months he held the post is unknown; the composer made only one cryptic reference to the Cathedral and Hofmann in his surviving letters (Briefe, iv:133–34), and no trace of his activities has yet been found in the diocesan and Cathedral archives, nor in the (mostly destroyed) music archive of St. Stephen’s. Mary Novello, recording her interviews with Constanze, wrote that Mozart played the organ of the Cathedral and was apparently engaged in directing music there (Novello 1955, 95, 113). It is possible that Mozart had the Cathedral in mind when composing Ave verum corpus, K. 618, or the fragmentary Kyrie, K. 323 (?1791).

In the event, Mozart predeceased Hofmann, and Johann Georg Albrechtsberger took over the assistant position and eventually became Domkapellmeister, allegedly with Mozart’s blessing (Briefe, iv:464). The fact that Albrechtsberger was appointed assistant on 12 Dec 1791, just a week after Mozart’s death, suggests that Hofmann was in genuine need of a deputy and thus Mozart’s involvement with the Cathedral may have been more extensive than the surviving sources suggest. (For more information on the context of Mozart’s appointment, see Weißensteiner 1991, and Black 2007, 251–301.)

Strangely, no surviving Viennese paper seems to have carried the news of Mozart’s appointment, and the only previous known reference appeared in the Pressburger Zeitung on 21 May (Dokumente, 347; Addenda, 66). Both the Pressburg paper and the Augspurgische Ordinari Postzeitung reported that the post of Domkapellmeister carried an enormous annual salary of 2000 fl. This figure is, however, inaccurate and misleading: the incumbent was paid only 324 fl in salary (Besoldung); an additional 1800 fl was intended for the upkeep of the Cathedral’s choirboys (Das Kostgeld für die Knaben). A lack of attention to this context has tripped up more than one modern commentator (see for example Landon 1988, 48). The Kapellmeister also received payments in kind and free lodging in the Kapellhaus, but the building was in poor condition and was demolished soon afterwards.

The report in the Münchner Zeitung, while not giving a salary for the post, includes an additional claim about the restoration of the Cathedral’s great organ. St. Stephen’s boasted four organs in Mozart’s time, of which only two were in anything like playable condition: the choir organ (Ferdinand Josef Römer, 1701) and the organ on the so-called “Füchsel” baldachin, next to the sacristy (Burchhard Tischlinger, 1507 and many later alterations), although the latter was also in decline. The great organ at the west door (Riesenorgel, Ferdinand Josef Römer, 1720) was never fully satisfactory: it was repaired in 1730 and again around 1770, and in 1779 Joseph Ogesser reported that because it had not turned out as well as hoped, it was no longer played (Lade 1990, 214).

From 1788 until 1793 there is a good deal of surviving correspondence regarding repairs and renovations to the Cathedral’s organs (Vienna, Archiv der Dompfarre, Erledigungen, Kartons 7 and 7a, and Vienna, Stadt- und Landesarchiv, HR A 17/4, 4/1789). In summary, the organ builder Johann Wimola the Younger (Jan Výmola, 1754–1800) was controversially commissioned to repair the sacristy organ in 1789 but in the course of his work determined that the instrument was not salvageable (even the famous piano builder Anton Walter complained about Wimola’s work on this project). Instead Wimola was to build a new instrument (II/34) in the case of the great organ, partially using pipes from the sacristy organ which was to be demolished for the purpose. It is this new organ to which the Munich report refers, but it could hardly be described as one of the largest instruments in the German-speaking lands; even in Vienna the celebrated Sieber organ at St. Michael's (1714, III/40), which Wimola renovated in 1784–85, was larger. Nor is the implausibly high cost of 30,000 fl correct: Wimola’s quoted price was 5,000 fl (a competing quote from the organ builder Franz Xaver Kristoph for a completely new instrument was 10,000 fl).

It appears that the work proceeded slowly. In Aug 1792 Wimola requested an additional 500 fl because he had been obliged for unspecified reasons to stop work for 15 months, which would put the cessation around May 1791 at the latest, just when the Munich report about the organ appeared, and Mozart was appointed adjunct Domkapellmeister. If the reason for the cessation was lack of funds, it is worth speculating whether the timing of Mozart’s application was more than coincidental and the composer sought to strengthen his case by requesting only an unpaid appointment. The renovated great organ, completed in 1792–93, continued to cause problems throughout the nineteenth century and was completely replaced in 1886. Römer’s original case of 1720 was retained (see illustration), but this perished along with the choir organ in a devastating fire in April 1945.