Ok...you know how half of the time I don't know what I'm talking about? Well, I guess this is one of those times.
I think what I meant to say before is that we can hear
overtones, not quarter or half tones. I'm still not quite sure if I'm explaining this right, but you know when you strike a key, you can hear not only the octave above it, but also the harmonic notes too. Like if you hit a low C, you can hear E, G, and the octave up C too - they ring out longer than the other notes. And supposedly, we hear all these overtones without realizing it. It's a characteristic that makes an acoustic grand superior to digital pianos. I don't even know if digital pianos generate overtones....I'm guessing they don't, which is why they always sound too 'clear' to me. (does that make sense?)
I do know that I cannot listen to organ music for very long because the 'overtones' (or half-tones, quarter-tones...whatever) make me nervous and sort of agitated to the point that I start to squirm a little.