In the mid-70s Chicago's venerable Association for the Advancement of Creative Musicians began to experience a slow and steady decline, brought on both by the emigration of its most influential members and, paradoxically, by the organization's own successes--in gaining wider acceptance for its music, the AACM obviated one of the reasons for its formation. But in the 80s a wave of younger artists began to arrive, dedicated to preserving and refreshing the AACM philosophy. And while I wouldn't want to burden any single band with the responsibility of leading that wave, no outfit would deserve that honor more than Ernest Dawkins's New Horizons Ensemble. Dawkins's sextet, founded in 1979, bridges new and old, and on several levels. Like the early bop bands, its front line of sax, trumpet, and trombone mirrors the sections of the swing orchestras, but the soloists (most notably the blazing trumpet man Ameen Muhammad) all speak a postfreedom improvisational language; on the other hand Dawkins has built a repertoire that pays far more attention to catchy themes, formal composition, and structural arranging than most "free jazz" groups would find comfortable. In the process New Horizons--which has a new album from the Swedish label Silkheart Records due this summer--does a grand job of reiterating the initial (but often forgotten) credo of the AACM, "Ancient to the Future." Dawkins himself has developed into a surefooted and frequently powerful soloist, spurting a hard-edged lyricism that depends as much on his clipped, asymmetrical phrasing as on the melodic contours of his flowing lines. Listeners may get a better dose of his alto and tenor work the first two Thursdays of this month, when he'll lead a trio; on the 20th and 27th, New Horizons takes up the cudgel. Thursday, July 13, 8 PM, HotHouse, 1565 N. Milwaukee; 235-2334.