I don't think music can be heard ICly. I'm pretty sure that's there because of how games are made and for ambiance. I wouldn't be opposed to someone ICly humming the tune of the song that's in  the background, though. But as far as if the song can be heard in the minds of the characters, I'll go with a "no".
Edit: Just found out about what Merri posted about. Hm. Did not know that.
Edit: Just found out about what Merri posted about. Hm. Did not know that.