Underworld rose from the semi-successful '80s synth-pop outfit known as Freur to become one of the great innovators in electronica. While the group's sound can easily be whittled down to its core elements--trance, dub, ambient, and a certain punkish fervor--the sum of Underworld's parts adds up to something more. Underworld's X factor may be Karl Hyde's vocals. With his half-spoken, half-shouted incantations, Hyde sings like a twisted gospel ranter gone mad in the DJ booth.