"Perfect" pitch isn't necessary, as slight deviations produce interesting sounds related to the "flanger" effect. It's the reason why pianos have more than one

"Perfect" pitch isn't necessary, as slight deviations produce interesting sounds related to the "flanger" effect. It's the reason why pianos have more than one string per key: it is the intention that they are slightly detuned, or else you wouldn't hear that there's more than one string. The deviation should preferably be less than, say, 1Hz, because you hear the difference in frequency as the beat frequency.