Piano Trio in B-flat major K.502

The piano trio was slower than the string quartet to develop as an important chamber music ensemble. This was partly due to the development of the piano itself, which was still the lightweight fortepiano and nowhere near the modern concert grand. This in turn affected the complex issue of balance given the unequal tone and dynamic properties of the three instruments, a balance that was constantly shifting as the instruments themselves changed. Early piano trios had been little more than accompanied sonatas, one step up from the Baroque continuo set up where bass instruments were brought in to reinforce the harpsichord. The accompanied sonata would primarily be a keyboard sonata with optional lines for cello and violin. We could safely say that in the last years of the 18th Century Mozart, Haydn and Beethoven between them created the piano trio out of the ruins of the Baroque trio sonata and the early classical accompanied sonata.

Mozart’s five trios in the period 1786-8 set things going, Haydn kept things moving in his London trios of the nineties and Beethoven’s three Opus 1 trios of 1795 finished the process. This afternoon’s concert features Mozart’s most admired trio form 1786 and the third of Beethoven’s bedrock-shaking trios from 1795. As with the six great string quartets dedicated to Haydn, Mozart’s sketches of the piano trios demonstrate that he struggled to get the balance right.

The opening Allegro borrows the idea of monothematic sonata form from Haydn. The unmistakable opening theme reappears as the second subject dressed up in a different key with varied scoring. Having got over this first surprise  and had it re-confirmed in the exposition repeat, Mozart springs a second surprise by beginning the exposition with a completely new and charming theme before bringing back the main theme in the minor. Much of this delicious movement owes its delight to its many reminders of the style of his great piano concertos.

The tender Larghetto speaks for itself, graceful and beauteous and dreamlike. The witty little rondo finale appears its appointed place and brings the Trio to a lively conclusion.