Andy Matuschak describes how the vibrations made in our ears vary between discordant and harmonious notes:
One hair cell will be stimulated over some small range of input frequencies: for instance, hairs for middle C (262 Hz), will also react to sounds between 230 Hz (roughly A?3) and 290 Hz (roughly D4). We’d say, then, that the critical bandwidth at middle C is around 60 Hz. Researchers have found that the bandwidth of a given hair equates to around a whole step on the western musical scale, basically the whole way up and down the keyboard.
Even though scientists haven’t yet worked out why this vibration affects us psychologically, he analyses how the harmonics produced when playing an instrument lead to discordant noises.