Complex sentence: The group had been playing all up and down the East Coast in clubs, and one night they were spotted by Clive Davis at the Whisky a Go Go (who at the time was the president of Columbia Records) signed them to the Epic Records label.
Split into simpler sentences: The group had been playing all up and down the East Coast in clubs, and one night they were spotted by Clive Davis at the Whisky a Go Go. Davis, who at the time was the president of Columbia Records, signed them to the Epic Records label.