The trombone isn't the most nuanced of brass instruments; chances are, if asked to imagine its sound, you'll get a sort of gaseous blurt in your head, one that most resembles an elephant's call. That's a shame, because the trombone is a truly great instrument, cleverly designed and beautifully executed, and in the right hands it can whisper with subtlety. Unfortunately, trombone players are few and far between, and the mere fact that they're digging on the trombone instead of the more popular brass instruments suggests that they're not your run-of-the-mill musician types. They want attention. So they blurt.
Chicago trombonist Jeb Bishop doesn't need to blurt, though he can do it with the best of them, as evidenced on his Jeb Bishop Trio (Okkadisk) recording. On it, he, drummer Tim Mulvenna and bassist Kent Kessler create beautiful, spacious free jazz. Bishop can murmur and mumble on his instrument, and when he cuts loose to improvise, he gracefully moves from frantic to fuzzy.
If you know of Bishop, chances are it's from his association with Tortoise, Stereolab, Jim O'Rourke, Gastr Del Sol, Ken Vandermark (Bishop's a member of the Ken Vandermark Five) or Peter Brotzman (he's a member of Brotzman's Octet and Tentet). Lots of activity, quite worthy of your attention.