Had things turned a little differently for Geoff Downes, the keyboardist would have gone down in history as merely the guy whose opening notes to the Buggles’ “Video Killed the Radio Star” kickstarted MTV, and an entire new era of music history, when the cable network launched on Aug. 1, 1981. But that song was just step one on a journey that brought Downes into the prog-rock supergroup Asia in 1982, where he co-wrote the immortal classic “Heat of the Moment,” and into Yes , where he’s served