They based this conclusion on the notion that no clarinets were available in Salzburg at that time and that Mozart must have brought back the pieces from his third and last Italian journey during the winter of 1772-73.
This notion, which was first asserted by Otto Jahn and then rather carelessly propagated by many scholars, has been put in considerable doubt by Kurt Birsak's research,[4] which revealed that clarinets were mentioned in an Aufsatz und Specification deren Spielleithen nothbetärftigen Instrumenten in französischem Thon [Essay and Specifications of the Instruments in the French Pitch required by Military Bandsmen] from 1769.
[5] However, Colin Lawson asserts that the writing for clarinet in K 166/159d (and to a lesser extent in K 186/159b) is incompatible with what would be expected from clarinettists in a mere military wind band, thereby adding credence to the theory that the works were inspired by an ensemble outside Salzburg.
[6] It has also been pointed out that the unusual scoring, most importantly the use of two English horns (Mozart had used them before only in the second version of the Divertimento K 113, also composed in Milan, and in La finta semplice, and after only in Il rè pastore[7]), strongly suggests a commission conceived for an already existing ensemble outside Salzburg.
[6] Further evidence for the kinship comes from the fact that in both pieces Mozart quotes from the ballet sketches Le gelosie del Seraglio K 135a (see below), now confirmed to have been composed by Joseph Starzer.
The main theme of the Andante grazioso, an almost literal transcription of an operatic sinfonia by Giovanni Paisiello,[6] is performed by the first oboe and first English horn an octave lower, supported by the bass.