Yesterday saw a major musical event: the arrival of a new instrument--actually a new, old instrument, as it is a reproduction of an 18th-century natural French horn. What a sound!
On this instrument every single pitch is colored with a timbre all its own relative to the natural overtones of the horn. Some of the tones are downright hilarious, others deeply poignant--very like a voice.
Perhaps that's why Mozart loved it so much. I have the feeling it colored his sense of pitch in all his writing, even for piano solo.
How mechanical we have become in relation to C-flats and such!