Mr. Jones used passages that seemed memorized, and they set up motifs through his solos, as if he were blocking off improvisational sections with riffs.

However, many of the pieces include large improvisational sections, where the instrumentalist is required to fill in the empty bars with their own melody to fit the standard chord progression listed above.

But halfway through the show, the songs blended together, and even the band's improvisational sections lost their interest.

Mr. Nieves, singing older material, turned the improvisational sections into a playground with a silver voice that made the melodies more important than the words.

Whenever that happens, rather than going back to the track I play something else that will fit, or I leave it as an improvisational section, so to speak.

That's how it happens, all those improvisational sections coming out - me forgetting what I played on albums and not going back and re-learning it.

Partway through a nuba, an improvisational section was played in the maqam of the following day to ready the audience for the next performance.

Mr. Lewis also expanded some of the improvisational sections.

The group cut the piece up into fragments, interspaced them with improvisational sections, and performed it live.

That conceit, which extended through the song's improvisational sections, nudged Mr. Wilson toward an excellent alto solo, both probing and playful in tone.