Monk often struck two neighbouring keys at once, a minor second. On a badly tuned piano that sounds like an accident. On his records it comes back too often, and too precisely, to be one.

The whole-tone run

A run down the whole-tone scale, fast, from the top of the keyboard, turns up at the end of chorus after chorus. It is one of the quickest ways to tell a Monk solo from anyone else's.

The gap

He would stop in the middle of a phrase and come back late, a beat or a bar after the band expected him. The rhythm section keeps going, and the tune carries on without the piano until he returns.

All musicians are subconsciously mathematicians. Thelonious Monk, DownBeat, 28 October 1971