How to account for the unusually mixed crowd that overflowed the tiny ICA Theater for a performance by John Tchicai with the Either/Orchestra last Saturday night? The Boston Creative Music Alliance concert series — of which this show was a part — usually draws a predominantly male mix of younger indie-rock types and conservatory kids with older jazzheads. But here were groups of well-dressed young women, a dad saving seats for his son and her girlfriend, twentysomethings on dates. All for a visiting avant-garde dignitary with a group of local jazz subversives.

The audience did get two hours of engrossing music — nine Tchicai originals of what might be called Africanized bop that drew on exotic meters and long-lined, minor-key melodies. Tchicai made the most of the E/O "little big band" set-up of 10 players, using percussionist Vicente Lebron and drummer Harvey Wirht as the foundation for a swirling mix of themes and counter-themes among the seven horns, with himself on tenor sax and bass clarinet.

The pieces unfolded in suite-like arrangements, in some cases with one composition moving onto the next without interruption. At times, those arrangements seemed ill-proportioned, with a solo bringing a piece to a halt before it had gotten off the ground. But on "Étude de Montséret," Rick Stone on alto sax and Henry Cook on flute shadowed each other in a rich duo deconstruction of the rhythmic kernel of Tchicai’s bopping theme, bassist Rick McLaughlin picking up on their ideas in a bowed solo of short, staccato phrases. In the second-set opener, the dance-like "Spirals of Ruby," Tchicai and E/O leader Russ Gershon engaged in spirited tenor-sax sparring, but the highpoint was trumpeter Colin Fisher’s mix of soaring phrases and nasty, smeared trills over the massed counterpoint of the band. The short "Not So Black" was based on a text by poet Ted Jones, with recitation by the band, to mixed success.

The jewel of the night was "Island Connection Suite," one of two compositions that Tchicai conducted rather than played on. Over another driving, motoric rhythm, his voicings sounded with tone-color specificity, from the high muted trumpets of Fisher and Tom Halter to Cook’s deep rocking baritone sax. There was a wonderful section for soprano, alto, and baritone saxes, semi-comic stop-start hand directions from Tchicai, and an ardent, virtuoso solo from trombonist Joel Yennior. It was very Tchicai and very Either/Orchestra. Here’s hoping they record it some day.