It's the composer, that's how a composer turns a small group into an organized ensemble.
I've never disliked him or the MJ@, but I really think that he last few years of the original run saw the band really finding another level.Starting with Blues at Carnegie Hall all the way through Blues on Bach. From 1966-1973. Things seemed to loosen up, breathe more, and Heath/Kay found some funk. It's by far my most consistently favorite MJQ.