In jazz, the rhythm section forms the heart of almost every ensemble, and the communication between rhythm section and leader helps determine the music's success. So when the rhythm section is the leader--as with TanaReid, the two-saxophone quintet assembled by drummer Akira Tana and bassist Rufus Reid--it simplifies matters considerably. One of the more versatile modern drummers, Tana has danced his sprightly, athletic rhythms across scores of recordings in recent years. Reid practically defines modern bass playing: musically, he's a direct descendant of Ray Brown in his ability to emphasize a large tone, finger-busting facility and unimpeachable taste in equal balance. It doesn't hurt that the remaining member of the rhythm section, the expansive and sometimes spiky pianist Rob Schneiderman, has led several terrific albums of his own. From the evidence of their new recording, Blue Motion (Evidence), TanaReid have grown since their last appearance here two years ago, at which time they had only recently added reedmen Craig Bailey and Dan Faulk; the lineup has knit impressively, and Bailey's flute has increased the band's textural range. The mix of solid and engag- ing musical personalities places TanaReid among the best mainstream groups you probably haven't heard of. Tuesday through next Sunday, May 29, Joe Segal's Jazz Showcase, Blackstone Hotel, 636 S. Michigan; 427-4846.