Of all instruments it's the saxophone that most closely resembles the human voice--with a potential only hinted at in the wailings of jazz players stuck in four-four time. Given this, it's odd that the possibilities of the all-saxophone choir went relatively uninvestigated for so long. That a saxophone quartet like Rova can be so constantly adventuresome without ever actually sounding all that esoteric only suggests how much territory lies unexplored. After 15 years Rova still gets compared a lot to the World Saxophone Quartet, but distinguishes itself from that foursome partly by its more "European" or "classical" sense of time and dynamics. For all the prowess of the individual players involved, it's Rova's group sound that dominates, whether what they're doing at, the moment comes more from the score or from their highly evolved ability to improvise collectively. It's very accessible, "musical" music, for no matter how texturally raw or contrapuntally complex Rova gets, the group always rides hard on that all-important implied connection with vocal song. Friday, 8 PM, Southend Musicworks, 1313 S. Wabash; 939-2848.