Too bad Rick Wakeman didn't stock around. When they recorded Space Oddity they were emulating what Paul McCartney and Ray Manzarek were doing at the time. Bowie played the drums and the guitars and Wakeman did the keyboards and bass pedals. Correct me if I'm wrong but Bowie and Wakeman never recorded a song again.
Wakeman plays on Changes,oh you pretty things and life on mars from Hunky Dory. Bowie invited him to join the band full time but later that day he got a call from yes. the rest is history
From Wikipedia: Bowie invited Wakeman to his home and played the outline of the tracks for him to learn; Wakeman later called them "the finest selection of songs I have ever heard in one sitting in my entire life"