I find it curious that Thelonious Monk's middle name was Sphere. What was that about? Perhaps no composer in the history of jazz has so often or so accurately been described as "angular." Monk always seems to be coming at the melody from an obscure, if not noneuclidean angle. Monk was one of the founding fathers of bop, and he remained within the compass of that music. But he was the greatest inspiration for the Avant Garde movement, which just couldn't get enough of Monk compositions. The link may be found precisely in his angularity. Avant Garde is distinct from Bop essentially in its abstraction. Every line in a bop number stands for some complex human passion. Avant garde abstracts from the passions to isolate the musical forms. I think Bop remains the greater music, but the jazz catalog would be poorer without the new thing.