Ludwig van Beethoven, Billet an Tobias Haslinger, Wien, nach dem 9. und vor dem 23. Januar 1817, Autograph

Beethoven writes to the publishing assistant Haslinger about several mistakes in the Sonata op. 101. For example in the last movement he would like the note "counter E" in the left hand to also be expressed in words. The note has many ledger lines and could only be played on modern pianos. The text was to increase the note's readability.

As far as the name of the instrument for which the sonata has been written is concerned, Beethoven wants to ask a learned person the same day. He is considering the terms "Tastenflügel", "Hammerflügel" or "Federflügelklavier".

Op. 101 was to introduce a series of more demanding piano music, the "Museum for Piano Music". Beethoven insisted on writing all the terms in the title in German, which is why it was taking him so long to find a suitable translation for the word "pianoforte". He even consulted an expert - the philologist Wilhelm Hebenstreit. The result of this search has become famous in connection with a later piano sonata (op. 106): Beethoven settled on "Hammerklavier".