The printed music in the CSU East Bay Library collection uses the Library of Congress call number system all beginning with the letter M. The printed music is generally arranged by the performance ensemble. That means that you can browse for all of the Brass Trios by looking at the music with call numbers beginning M 357. Of course M 357 is the call number for ALL instrumental trios, but still, it's a way to start looking for what you want.
Here's a general guide to instrumental ensemble music call numbers:
There are other ways to locate specific ensemble and solo music and I hope you'll consult with me anytime you have a question about that. My contact information is in the box at the right of this page. I look forward to your questions! -Tom