You say you’re looking for a musical experience that’s really–despite overuse of the word–unique? You say you really do give a hoot about that fabled Rubicon between the jazz and classical avant-gardes? And you want to actually enjoy the occasion, too? Then you’d be crazy to miss this weekend’s performances by ROVA, the San Francisco-based saxophone quartet. Combining the shock of the new with the traditional sonorities of a finely tuned sax section, ROVA can be counted on to try almost anything, and to make it sound good in the process. (In fact, the quartet’s most innovative music has a deceptive familiarity: it welcomes rather than repels unsuspecting listeners.) At the age of 13, ROVA still places more emphasis on composition than many of the sax ensembles that have followed in its wake–which is not to deny the committed and purposeful improvisation that also distinguishes the group. This is music making of a very high order. As is often true of such music, there’s a rich if sly humor lurking around the edges; it should be especially evident in Sunday’s performance, when ROVA will improvisationally “interact” with the booming acoustics of the neo-Gothic Bergman Gallery, and also with the Niele Toroni installation currently on display there. Saturday, 8 PM, Southend Musicworks, 1313 S. Wabash; 939-2848. Sunday, 4 PM, Renaissance Society, Cobb Hall, University of Chicago, 5811 S. Ellis; 702-8670.