Tvad, Brian Epstein is the one who made them change from Levis and leather jackets to a more "respectable" look (enter the famous "Beatle Suit"), so isn't HE the reason that modern music exists? :)
Would music be the same today if not for the Beatles? That's akin to having Clarence the guardian angel show George Bailey what the world would have been like had he never been born. Music would certainly be different, but in what ways you can never know. Who knows, music might be better, had the Beatles never existed. Maybe their presence squashed the rise of another band that was going to have an even more profound effect?
Just think, if there had been no Beatles, there would be no one to sue Apple Computer all the time. And life without litigation just ain't worth livin'. And if there had been no Beatles, none of us would ever have heard Yoko's "Kiss Kiss Kiss Kiss Me Love". :)
Cheers