Franz Xaver Gerl have been the composer of the aria "Ein Weib ist das herrlichste Ding", for which Mozart wrote a set of variations for piano, K. 613 (the composer may instead have been another singer-composer in the troupe, Benedikt Schack). Mozart gradually came to participate more in the activities of the Schikaneder troupe, culminating in his opera "The Magic Flute" (1791), with libretto by Schikaneder. Gerl premiered the role of Sarastro, and continued to sing this part in many performances through 1792. He left Schikaneder's troupe in 1793. Gerl may have been a participant in a rehearsal of Mozart's "Requiem" on the
Piano concertos by Wolfgang Amadeus Mozart it was probably J.C. Bach, whom Mozart admired, who introduced the structural innovation of allowing the keyboard to introduce new thematic material in its first entry. Concertos Nos 1–4 (K. 37, 39, 40 and 41) are orchestral and keyboard arrangements of sonata movements by other composers. The next three concertos (K. 107/1, 2 and 3), which are not numbered, are arrangements of piano sonatas by J.C. Bach (Op 5. Nos. 2, 3, and 4, all composed by 1766). Based on handwriting analysis of the autographs they are believed to date from 1771–72. Concerto No. 5, K. 175 from 1773 was