Like countless parents before him, Steven Tyler is shocked at the music that's been blaring out of his fifteen-year-old son's bedroom lately. But the Aerosmith frontman can hardly disapprove. "I walk by at night and my son is listening to Zeppelin stuff, like 'Black Dog,'" Tyler says. "He's turned all his friends on to Cream, and they're all into [Aerosmith's] Toys in the Attic. I told him, 'I can't believe you're listening to this.'" Though classic rock is in no danger of edging out emo and hip-hop on most teenagers' playlists, a growing number of kids are also making room...