His "jungle music"phase or whatever it's called. It was rawer and not as sophisticated as his later stuff but the finesse was there...

Anyway, jazz-artists in general are mostly revered for their middle work. In their early stage, they have often not found a personal style yet and the technique toll off the ideas they have convincingly may be lacking. As for the later stuff, prior to the whole Wynton-scene, jazz-criticism has largely favoured artists that have been (semi) cutting edge for their time (see: the reason why so little straight jazz from the 70's is revered) and by default, aging artists have suffered because of this...