http://pc.ign.com/articles/116/1163104p1.html
Won't be music in-game like some have asked about, but it is mentioned every gun has a different sound, to increase the chance that many guns firing at once will make a "choir."
Other interesting stuff in there too. Every class makes a different sound running, and clothing options can alter this sound. Medics are the only ones to hear other players calling for help, soldiers hear requests for ammo, etc. Enjoy.
Edit: Just read more, another interesting fact. If an ally is at the other side of the map, their character will use their radio over the auto-pvssyr. Over this radio, you can hear what's going on by them. For instance, you are a medic who just spawned, and a friendly soldier was incapped in a firefight by the objective. When his character automatically called "Medic!!!" or whatever, you would not only hear his voice through a radio, but you would hear the bullets and explosions going on around him.
Wasn't really worried about sound, not a make-or-break thing, really, but Splash really went all out.