BoxRec

It was nominated for an Academy Award.
Produced by Bill Cayton and directed by Jim Jacobs
.Soundtrack by Miles Davis.
Brock Peters narrated as voice of Jack Johnson.
Is or was this 1970 documentary released on video or DVD?
Why was the 1970 American release(90 mintues)
two minutes longer then the British release(88 minutes)?

Its probably longer because PAL and NTSC run at a different frames per second.

One of the most common reasons bits are cut out of films is due to copyright problems conserning music played in films.

Miles Davis did the soundtrack for the documentary,but its all through it I understand.

The soundtrack album is good. It has an actor narrating Jack Johnsons own words at one point. Nice funky freeform music, good with a bifter.