Here’s Miklós Spányi on the Probestücke
In my opinion it is no exaggeration to say that C.P.E. Bach's eighteen Probestücke, grouped as six sonatas and published as an appendix to his epoch-making keyboard treatise Versuch über die wahre Art das Clavier zu spielen, are among the most substantial works in the composer's entire keyboard oeuvre. Although Bach's keyboard music shows an amazingly constant high quality it also has some extraordinary high points. I am prepared not only to rank the set of the Probestücke among these, but also to propose it as a pinnacle in the entire literature for the keyboard.
C.P.E. Bach's publications with pedagogical aims show that he never found composing for less skilled or amateur players or even beginners a burden but rather a special challenge, resulting (as in the case of some other brilliant key-board educators such as Johann Sebastian Bach or Bela Bart6k) in excellent pieces. But even among C. R E. Bach's pedagogical works the Probestücke hold a special place. In this publication Bach collected his most precious ideas, as if to demonstrate his finest skills as composer and pedagogue as well as his ideas about the aesthetics of keyboard playing: an hour's worth of music of pure beauty, full of the most varied and sparkling ideas. In most cases I have even refrained from adding embellishments to the repeats in binary movements in order to pre-sent these musical diamonds in their original, unadulterated, marvellous glow.
Even technical restrictions did not discourage Bach: the Probestücke are composed so that they could be played on less modern instruments of the time, with a keyboard range of only four octaves. We also know, from the text part of the Versuch, that Bach did not rule out the performance of the pieces on the harpsichord or other keyboard instruments although his preferred instrument was the clavichord. The Probestücke also contain some indications of Bebung, an effect similar to vibrato on string instruments and only possible to achieve on the clavichord among the keyboard instruments. At the time of composition of the Probestücke, more modern clavichords were being built with a five-octave compass. As the Versuch as well as the Probestücke remained relevant until the end of the eighteenth century (or even longer), I believe that the choice of a clavichord modelled on an instrument of the late eighteenth century is one of the possible historically correct choices. After much experimenting, my conclusion is that my large, late-Saxonian clavichord is a very convincing instrument for the Probestücke. Despite of its powerful and robust sound, the most delicate effects required by these compositions can be achieved on it. This is, however, only one of the numerous types of clavichord and keyboard instrument in general on which this music may have been performed in its time.