Lagniappe: Planned Improvisation

She glanced back at where my dad ... was having a technical discussion with the rest of the band. Lots of hand gestures as he indicated where he wanted solos to come in during the set because, as my dad always says, while improvisation and spontaneity may be the hallmarks of great jazz, the hallmark of being a great player is ensuring the rest of the band is spontaneously improvising the way you want them to.

Ben Aaronovitch, Broken Homes

Aha! I always suspected as much!