This is a play on words. "Bach" is the the name of a famous classical composer but sounds like "bark" as in the famous expression "his bark is worse than his bite" . Vampires are known for biting but since the vampire tortured his victims with music, his "Bach", or the classical music he plays, is worse than his bite.
Did you hear about the vampire who used to torture his victims with music ? His Bach was worse than his bite .