We've talked here about studio musicians and rock docs. I'm gonna pound the drum again for "Standing in the Shadows of Motown", an Oscar winning documentary about the Funk Brothers, the Motown house band. When Motown was still in Detroit these guys were the house band, laboring down in the basement of the little house that was the home of Motown. They took the charts the various songwriters and producers brought in and cut the instrumental track. The producers would then decide which artist was going to get the song, in some cases having several different vocalists/groups sing it, then picking the one who felt best. When Berry Gordy moved Motown to L.A., all these guys were left behind in Detroit. Over the years they scattered, playing in little jazz clubs, driving taxis, supporting themselves as they could. Many years later the film makers went to Detroit and hunted them up, filmed interviews, chatted them up and got their stories. They also set up a concert, with the Funk Brothers backing a number of singers singing the old Motown songs they played on.
These guys played on literally hundreds of songs that we know by heart. Anyhow, I ran up on this during a Youtube crawl, so I'ma give you a taste. Hunt up the film if you have not seen it, it's damn good work.