Mark McKeever was the original pianist for the Polyphonic Spree, playing keyboards from the very first show. His setup, consisting of a Korg N5 and a Moog Rogue, was maintained by Joe Butcher when the latter joined the Spree upon McKeever's departure in Spring 2003. Mark McKeever also played trumpet alongside Chris Curiel on La La. These two former Spree members would later perform together in the band Swerve.
Mark McKeever is married to Christy Stewart, former member of the Polyphonic Spree choir.