The piano music of Mozart has qualities which call for a very specific piano. The speed of action, lightness of touch and dynamic range of the Viennese fortepiano have long been associated with the pianos of Johann Andreas Stein and his contemporaries. Wolfgang wrote a glowing and comprehensive report of their excellence, and especially interesting is the emergent musical detail. It is their reliability and lack of annoying quirks which distinguished them: their lack of power and sheer volume was never seen as a deterent to the most affective and virtuoso music. In his Sonatas Mozart effectively established piano style for generations. By employing elements of theatre music, harpsichord texture and ornament, and the harmonic devices of the orchestra, he established a self-contained keyboard universe.

By listening to the contemporary piano Sonata in E-flat by Josef Haydn, and the earlier music of J.C. (the "London") Bach, it's easy to understand the blank canvas that an instrument such as the new piano offered. Using their favorite idioms, for Haydn the string quartet, for J.C. Bach the open-textured opera-aria style, these composers made far different choices from Mozart, but found an equally effective answer. Haydn stretches the form of the Sonata far from its original shape, but Bach remains almost tersely within it, able to make simple ideas melodically memorable.