Sort Of Like Harmony

A reader of Rifftides or Take Five (both, I hope) has been listening to Jim Hall’s 1974 Concierto CD in which Hall’s sidemen are Paul Desmond, Chet Baker, Roland Hanna, Ron Carter and Steve Gadd. She sent a message asking a question at which musicians tend to guffaw when civilians ask it, one that arises out of genuine interest and does not deserve scorn. Here’s the exchange:
Q: The track “Concierto de Aranjuez” is hauntingly beautiful. Do the musicians totally improvise, or do they each have a kind of musical outline around which they create? You can guess from the question I’m not a musician, but it’s something I’ve wondered about.
A. Except in the most unfettered avant garde improvisation, there must be a plan or the result will be random noise, which, come to think of it, describes the most unfettered avant garde improvisation. Virtually every piece of music has some sort of tonal organization, whether or not there is a formal chord structure. In the case of “Concierto” on the Jim Hall album, the musicians improvise around the simple and quite lovely harmonies that Joaquin Rodrigo wrote into the adagio section of his famous “Concierto de Aranjuez.”
Jazz musicians frequently get questions about whether they know what they’re doing. In Take Five: The Public and Private Lives of Paul Desmond, I included an old Down Beat piece of mine that tells how Paul dealt with the question on one occasion. it’s on page 214. Here is the pertinent passage.

Desmond and an old friend were about to reminisce, but one of the Musicarnival actresses had a question.
“I don’t want to show my ignorance,” she chirped, “but do you know what you’re going to play before you sit down, or do you just sort of make it up as you go along?”
Desmond gave her a long look to be sure he wasn’t the victim of a put-on, decided he wasn’t, and explained.
“First of all, I never sit down. But I do try to follow a general plan, which we’ve all discussed on the plane. Chords and things.”
“Oh, you mean sort of like harmony.”
“Yeah, something like that.”