It has never attained the popularity of the World Saxophone Quartet, but San Francisco’s ROVA sax quartet has been setting the parameters of the format for 20 years now. In anticipation of its anniversary the group–with all the original players save Andrew Voigt, who was replaced in 1988 by Steve Adams–has been working at a feverish pace: over the last year and a half it has released at least five recordings and collaborated with a broad array of outside composers and musicians. On the two volumes of The Works (Black Saint), members Adams, Larry Ochs, Bruce Ackley, and Jon Raskin perform pieces by Tim Berne, John Carter, Jack DeJohnette, and Fred Ho. And when they decided to record a version of John Coltrane’s chaotic, cathartic masterpiece Ascension, they enlisted the help of folks like trumpeters Dave Douglas and Raphe Malik, pianist Chris Brown, and bassist Lisle Ellis. While much of ROVA’s work leans on the rich contrapuntal arrangements and edgy improvisations of the best postbop and free jazz, the quartet also liberally borrows from more modernistic traditions, including the experimental soundscapes of early AACM figures like Anthony Braxton and Roscoe Mitchell and the academic, minimalist work of contemporary classical artists–they’ve performed music written by Terry Riley and collaborated with electronic composer Alvin Curran. ROVA only comes through Chicago every three or four years, and its performances are routinely mind-blowing. Friday, 8:30 PM, Unity Temple, 875 Lake, Oak Park; 708-383-8873. PETER MARGASAK

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