Whether or not the World Saxophone Quartet, formed back in 1977, triggered the wave of four-reed, no-rhythm-section jazz ensembles that crested in the early 90s, no one would deny that it was one of the idiom’s brightest beacons. The quartet collected the best of the avant-garde saxists who converged on New York in the mid-70s–alto-soprano men Julius Hemphill and Oliver Lake, baritone saxist Hamiet Bluiett, and tenorist David Murray. They used the harmonies of classic doo-wop as ballast on their wilder flights; dressed in top hats and tails, they knew how to entertain as well as challenge. But the group has yet to address the loss of Hemphill, its de facto leader and guiding genius, who left the band in 1990 and died in ’95. Replacing him means more than just replacing his horn in the mix, a job first undertaken by Arthur Blythe and now by John Purcell. It also means finding a new conceptual framework as viable as the 21st-century blues ‘n’ roots expressionism he brought to the band. The WSQ’s last two albums have reflected this ongoing search, departing with mixed results from the trademark economy of its a cappella saxophone singing: Four Now (Justin Time), from 1996, featured a trio of African drummers, and in 1997 Takin’ It 2 the Next Level diluted the power of the reeds with a conventional piano-bass-drums rhythm section. But a WSQ performance still offers the chance to hear three utterly distinctive saxophone personalities at work: the astringent rigor of Lake’s alto, the outsize virtuosity of Murray’s tenor and bass clarinet, and the graceful belch of Bluiett’s lower register. Their appearance marks a departure for Steppenwolf’s “Traffic” series in that it doesn’t attempt an interdisciplinary fusion; accordingly, the evening reverts to a typical nightclub schedule, with two discrete shows instead of a concert with intermission. Monday, 7 and 9:30 PM, Steppenwolf Theatre, 1650 N. Halsted; 312-335-1650. NEIL TESSER

Art accompanying story in printed newspaper (not available in this archive): uncredited photo.