Musical tone and perceived dissonance

Why does a perfect fifth sound so satisfying when a brash tritone is just a half step away? It seems we have a physiological correlate to these psychological effects. As sounds arrive, the basilar membrane vibrates like an oblong drum head, stimulating tiny hair cells attached to nerves. Each hair cell corresponds to a perceived frequency, working like little band-pass filters. One hair cell will be stimulated over some small range of input frequencies: for instance, hairs for middle C (262 Hz),...