I'm trying to understand your reference to the the tone that we call the note of "C" ,not sounding like "C" based on the instrument, or two different individuals playing an instrument, of which you use the guitar and piano as an example. I believe "C" vibrates at 440 hz regardless of who is striking the note;yes? Piano and guitar have different tonal qualities, as does a trumpet compared to a violin, but a "C" is still a "C", and thus vibrates at the same rate, if that "C" is played in a the same octave range. It'a an interesting point that you've brought up though.
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