Many enduring musical works have been born out of close relationships between composers and performers. The clarinet-playing Stadler brothers were among Mozart’s good friends, and their talents enabled him to realise exploratory writing for one of his favourite instruments. Mozart was the first composer to exploit the clarinet’s full range and versatility, and is credited with establishing the instrument as a mainstream chamber music instrument.

The Stadler brothers both played in the Vienna Court Orchestra, and Anton Stadler, in particular, was a well-known virtuoso with exceptional mastery of the clarinet’s lower register. The Trio in E flat, along with Mozart’s Clarinet Quintet and his concerto, were written especially for Stadler to perform.

In this trio, the then unusual combination of clarinet, viola and piano enabled Mozart to play with the traditional roles of each instrument. It was standard at the time for the lowest instrument to double the bass line of the piano part. But here, as in the K. 496, Mozart creates a more independent character for each instrument and continues to experiment with various group dynamics.

Replacing the violin with the clarinet gives the trio a slightly broodier, more romantic sound, and this mood is intensified by the choice of a slower tempo in the first movement rather than the usual sprightly allegro. The opening decorative figure later becomes the accompaniment to the second, more lyrical theme introduced by the clarinet.

The second movement begins as a minuet and trio, but the trio takes a major detour in exploring its simple theme, becoming completely engrossed in the possibilities before eventually returning to a restatement of the minuet’s theme. The final movement is a rondo built on the second theme from the first movement, with more elaborate decorations added after each contrasting episode.

The trio is commonly called the ‘Kegelstatt’ trio – meaning skittles lane, or bowling alley – in reference to the popular rumor that the trio was written while Mozart was out bowling with friends. There is no evidence to support this idea, but the name could well be a jocular reference to Mozart’s prodigious creative output around this time. In 1786, the year the trio was written, Mozart also wrote two more piano trios, the opera The Marriage of Figaro, two piano concertos and various other pieces of chamber music.