Judging by appearances, Brahms and Mussorgsky had a lot in common - beefy frames, long hair, full and scraggly beards, a fondness for the occasional (OK, in Mussorgsky's case, the perpetual) drink. But, musically, these contemporaneous composers were pretty much on separate planets.
Brahms, a standard-bearer of German conservatism, brought to the standard structures - symphony, concerto, sonata, chamber works - a wealth of lyricism and refinement of technique. Mussorgsky, the Russian radical of his day, didn't bother with those old structures, focusing most of his energy on opera (a genre Brahms avoided). And he pretty much wrote as he pleased, without regard for anyone else's preconceptions of harmony and melodic contour.
If you go The BSO performs at 8 tonight and 3 p.m. tomorrow at Meyerhoff Symphony Hall. Tickets are $25-$78. 410-783-8000 or baltimoresymphony.org.