Complex sentence: Most of the footage comes from 5 sessions of Prince and Smith discussing the music with fans rests in Prince's vault, while some was used originally to promote "The Rainbow Children" album and for background video at his live concerts.
Split into simpler sentences: Most of the footage comes from five sessions of Prince and Smith discussing music with fans. The footage still resides in Prince's vault, while some was used to promote "The Rainbow Children" album and as background video at some of his live concerts.