i think i may remember the interview you’re talking about. don’t know for sure what he meant. my guess would be that there are habitual vamps, modulations, and substitutions that improvising groups fall into over time within given songs or during sections of their act, and that that these familiar jumping-off points for improvisation may be what he meant by the word “pillar”. i guess the reason i think it refers to familiar/fertile interpersonal improvisation patterns within the group (rather than being about some of the other more explicitly technique-oriented things mentioned) is because it’s the only real “X” factor i can think of besides inspiration itself. other facets of technique & performance have specific names — names which as a rule jerry seemed to use when he talked about them in interviews. he was more open and eloquent about how and what he worked on in private practice than most famous musicians so i assume that if he knew of a clearer way to describe his experience he would use it. but of course maybe i’m wrong about it too, just my guess.
but also +1 on the importance of ear training, lexicon, technique, and the interesting piece on improv which was linked to.