Beethoven on the development of the piano as an instrument in its own right:
There is no doubt that so far as the manner of playing it is concerned, the pianoforte is still the least studied and developed of all instruments; often one thinks that one is merely listening to a harp. And I am delighted, my dear fellow, that you are one of the few who realize and perceive that, provided one can feel the music, one can also make the pianoforte sing. I hope that the time will come when the harp and pianoforte will be treated as two entirely different instruments.
Beethoven, in a letter to Johann Andreas Streicher, 1796.
Anderson, Emily, ed. (1961) The Letters of Beethoven. 3 Vol., London: St. Martin’s Press. Letter 18. Cited in: Marek, George (1969) Beethoven: Biography of a Genius. London: William Kimber, p.161.