Firmly entrenched in jazz’s avant-garde, flutist/alto saxophonist Henry Threadgill isn’t terribly approachable with his compositions at the forefront. When he puts the emphasis on group improvisation, as in his Zooid band, things get even more opaque: The uniquely orchestrated quintet (electric guitar, cello, tuba and drums alongside Threadgill’s horns) created a knotty, fluctuating wall of dissonant noise at the Library of Congress’s Coolidge Auditorium on Friday night. Still, there was an easy foothold for the audience: a powerful groove.

Zooid’s set consisted of six tunes, each so dense and atonal that if they hadn’t broken for applause in between, it would be difficult to tell the difference. The musicians’ shifts in approach didn’t clear things up, since those shifts were constant. Cellist Christopher Hoffman moved from bow to pizzicato in the opening “Chairmaster,” then vice versa in the following “Tomorrow Sunny.” Meanwhile, Liberty Ellman relied mostly on dark, single-note guitar lines, but could sporadically erupt into a salvo of brambly chords; on “A Day Off,” he blended the two devices into a caustic mix that virtually scraped across the tune. The most definitive changeovers were in the horns: Threadgill played flute for the first three pieces, then swapped out its ethereal, catlike grace for the urgent wails of his alto sax in the last three. Jose Davila, meanwhile, put aside his pulsing tuba to feature plunger-muted trombone on the third selection, “To Undertake My Corners Open.”

The groove, long a core of Threadgill’s music, both unified the set and delineated one tune from the next. It became something of a game to determine what time signature drummer Elliot Kavee was busily playing in: 6/4 on “Tomorrow Sunny,” 7/8 on “Not the White Flag,” undulating 4/4 on “Ambient Pressure Thereby.” Kavee’s time wasn’t necessarily the yardstick for a piece; in most cases, each musician layered a different time over him — Davila accenting Kavee, Ellman accenting Davila, Hoffman accenting Ellman — Threadgill then penetrating with a line that somehow accounted for all of them. (On “A Day Off,” Threadgill’s entry made a churning rhythmic brew suddenly coalesce into James Brown-style funk.) But it was the drummer that most held the crowd in thrall: A look around the auditorium revealed a roomful of tapping feet, all moving to Kavee’s beat.

Even Threadgill, keenly watching over the proceedings (when not playing) like a sensei observing his karate students, couldn’t help bobbing his shoulders. It was intoxicating.

West is a freelance writer.