When Western ears first encounter the vocal stylings of Pandit Pran Nath, the greatest living exponent of the classical tradition of northern India known as Kirana, what immediately stands out is the low, rich droning sound. At first, much of his music sounds repetitious and unchanging, although this is an aural illusion; the music is constantly shifting in pitch, timbre, and expression, but never in its incomparable beauty. Indian scales (or ragas) contain subtleties of pitch that are often undistinguishable to ears used to Western singing (which, because of its emphasis on projection and large sound, tends to be sloppy about pitch). The result--at least in the case of a master such as Pran Nath--is a majestic sound that sweeps you off your feet. Pran Nath has disciples all over the world, but his chief secular influence lies in the fact that creators of minimalism such as La Monte Young and Terry Riley have been his longtime pupils. Riley himself will be on hand to accompany his master on tambura as part of a three-piece band. Monday, 8 PM, Royal-George Theatre, 1641 N. Halsted; 242-6237.