First Born: Al Downing: I'll Be Holding On (1974)

Well, maybe not the first, but one of the first available to the public (..or Tom's friends at least). Al Downing: "I'll Be Holding On" (1974) was edited by the magnificient Tom Moulton (picture) and cut on acetate 10". However, it wasn't release until 2006 on the Soul Jazz comp "A Tom Moulton Mix"
A typical cut'n'paste mix - by far his best - but nevertheless a good example of the possibilities of the time.