Divertimento (Piano Trio) in B flat, K.254

When Mozart wrote his Divertimento in B flat - in Salzburg in 1776 - the piano trio was not the integrated ensemble it was later to become. The title under which it was published in Paris in 1778 says it all, if in fairly fanciful French: “Divertimento pour le clavecin ou forte-piano a Compagnemment violino a violencello.” In other words it was presented as a keyboard work with accompanying parts for violin and cello. That was the state of the art as practised at the time by, among others, C.P.E. Bach, Michael Haydn and even Joseph Haydn, all of whom had written piano trios which with little adaptation could be performed on the harpsichord or piano alone.

As Joseph Haydn was to go on doing into the 1790s, Mozart keeps the cello tied more or less firmly to the bass line here. The violin enjoys rather more prominence but little real freedom. It is the piano that introduces both the main themes of the first movement while the violin fills in the harmonic background or adds a few contrapuntal details and only rarely produces a melodic idea of its own. This treatment of the strings does not, of course, reduce the interest of the short development section, with its striking changes of harmony and dynamic colouring, and it is positively effective in offsetting the brilliance of the keyboard writing.

The Adagio, on the other hand, is more like a dialogue for violin and piano. While the cello remains comparatively subdued, the violin introduces the tender main theme in E flat major and, although the piano is awarded the second subject, it is the violin that inspires the most surprising harmonic diversion in the development section. In the Tempo di menuetto finale, moreover, the violin not only has first use of the rondo theme but also keeps it to itself until after the first episode, at which point violin and piano formally exchange the roles they had played at the beginning of the movement. As for the cello, although it is still denied all melodic interest, it briefly draws attention to itself in the second episode with a solitary example of pizzicato colouring applied to its customary support of the bass line of the piano.