Complex sentence: Cook had been the keyboardist for the band Spring Canyon, which had recorded an album for Warner Brothers a few years earlier with producer Richard Podolor which was never released, due to a change in management at Warner Brothers.
Split into simpler sentences: Cook had been the keyboardist for the band Spring Canyon, which had recorded an album for Warner Brothers a few years earlier with producer Richard Podolor. That album was never released due to a change in management at Warner Brothers.