Hieronymus Graf von Colloredo commissioned Haydn to write six duos for violin and viola. Haydn fell ill after completing the fourth, so he asked Mozart to write the other two (K. 423 and K. 424). The set of six was presented as all Haydn's, and Colloredo was unable to "detect in them Mozart's obvious workmanship." Duo for violin and viola in C major, Perger 127, MH 335 Duo for violin and viola in D major, Perger 128, MH 336 Duo for violin and viola in E major, Perger 129, MH 337 Duo for violin and viola in F major, Perger 130, MH 338 Solo sonatas 6 Menuetti for violin and continuo, MH 210 Divertimento for flute and harpsichord in G major, MH 273 Keyboard Allegretto in F major, MH 471 Allegro in G major, MH 470 Andante in C major, MH 466 Anweisung von einem Haupt-Ton in alle übrige Töne zu kommen, MH 318 Beispiele zur Übung im bezifferten Grundbass, MH 433 Cadenze e versetti (fragment), MH 435 Cadenze e versetti, Perger 131, MH 176 Canonic studies, MH 568 Contrapuntal studies, MH 177 Contrapuntal studies, MH 434 Deutscher Tanz in A major, MH 465 Gewöhnliche Signaturen des Generalbasses, MH 317 Menuetto in E minor, MH 472 Menuetto in F major, MH 469 Piece in D major, MH 467 Piece in E-flat major, MH 468 Preludes and Finale, MH 436 Variations in C major, Perger 132, MH 108a Variations on 'Gott erhalte Franz der Kaiser', MH 771 Unknown instrumentation Piece in C major without title, MH 571 Sacred vocal music Antiphons Alma Redemptoris Mater in A major, MH 103 Alma Redemptoris Mater in D major, MH 164 Alma Redemptoris Mater in D major (fragment), MH 92 Alma Redemptoris Mater in D major (K V:19a), MH 637 Alma Redemptoris Mater in E-flat major (K V:19b), MH 270 Alma Redemptoris Mater in F major, MH 163 Antiphonarium Romanum, MH 533 Ave Maris Stella in G major, MH 49 Ave Regina in A major, MH 14 Ave Regina in C major, MH 227 Ave Regina in C major (K V:14a), MH 140 Ave Regina in E-flat major, MH 127 Ave Regina in F major, MH 457 Ave Regina in G major (K V:14b), MH 650 Crucem sanctam in B-flat major (K V:10), MH 201 Deutsches Alma Redemptoris Mater in D major, MH 676 Deutsches Ave Maris Stella in G major, MH 677 Deutsches Regina