Many of those sessions included Warren's friend Mark Kibble, also an accomplished arranger, pianist, and vocalist (and future member of Take 6). As early as the age of 13, Warren and Kibble, who were born five weeks apart, had performed concerts together, singing solos and duets, while taking turns providing accompaniment at the piano. One of the duets began with Warren singing and Kibble at the piano; then, halfway through the song, Warren would leave the stage and take over at the piano, seamlessly, at which point Kibble would take the stage to sing.