The Urf music in particular seems fairly loudly recorded, but I'm pretty sure most all of the launcher musics I've heard since I started playing have been on the loud side. The mouse click sounds seem normal/quiet but the music is just BOOM!
Good ears mate. We noticed this too and are looking into it. I think the URF music was mastered slightly different than regular logins and we think that there may be something in the launcher code that is adding additional gain stages that are unnecessary, especially for the URF music. I think someone is looking into changing that.
Thanks for bringing this up! Having something blast your ears is definitely not fun. :( We're really sorry about that. Like Utora mentioned, we've been working on tracking down what caused the exceedingly loud volume on this particular login. The track itself was mastered at a normal level and is quieter than what comes out of the launcher at default settings, so something somewhere in the code is boosting the track past its nominal level.
You can change the League volume in your options.
The music is indeed real loud.. But the song rocks so it's acceptable :D 
Yeah, the launcher music is so much louder than the in-game sounds.
It's a pain to manage sound levels all the time.
