If you look at the lineup, you figure you know the band; after all, the combo of saxophone, electric bass, percussion, and one of those ubiquitous multipurpose keyboards--which has come to spell "fusion"--can be found in high-tech nightclubs all across this great land. What sets Mark Colby and Frank Caruso apart from the pack is a mixture of craft and commitment. The music has heft; powered by Colby's horn work, which itself was honed during stints with Maynard Ferguson, Jaco Pastorius, and Bob James, it displays subtlety and restraint in addition to the more common virtuosity and swagger. The former qualities give meaning to the latter. Not the least interesting aspect of this band is its material; Colby and Caruso play some of their own tunes, of course, but they also perform songs by their contemporaries, jazz (and jazz-based) composers such as Randy Bernsen, Andy Laverne, and the late Mike Lawrence. In this way, they have built a repertoire that puts the last dozen years of "fusion," or "contemporary jazz," or whatever the hell you want to call it, into some sort of perspective, and allows them to legitimately build on whatever "tradition" can be said to have evolved. Such an approach does more than codify the idiom: it gives Colby/Caruso a variety that any number of more self-centered bands would do well to cultivate. Wednesday, the Bulls, 1916 N. Lincoln Park West; 337-3000. Thursday, Cairo, 720 N. Wells; 266-6620.