"MOSTLY GABRIELI." Chicago Chamber Brass. Pro Arte SDS-632. In an already overcrowded market, here is still another collection of Renaissance brass music. It's no secret that the Gabrielis unknowingly anticipated the stereo era with their antiphonal brass canzonas. What now appears evident is that they also seem to have anticipated the digital era. The Chicagoans' warmly blended sound emerges with utter clarity, yet the recording permits the listener so inclined to focus on one voice at a time. The music is fairly standard stuff: lots of harmony, lots of counterpoint and scarcely a single memorable tune. The players, incidentally, will appear in concert at Cal State Long Beach on Tuesday night.