How about Lucio Berio, the avant-garde modern classical (or whatever one calls post-Stravinsky stuff) Italian communist composer. Or, Frederic Rzewski who after the Chilean coup in '73 wrote, "The People United Will Never Be Defeated!"Or the work of marxist (see his anthology, "Marxism and Art, " from Vintage/Random House sometime in the early 70's) Beethoven scholar, Maynard Solomon???
Michael Pugliese (who himself would rather listen to The Clash or The Gang of Four)