milos foreman's Hair(1979)
Mr. Foreman thought: let's make a spectacular musical where we can not only patronize all the generational conflict, sex, the draft, race issues, drugs, and the american army, but also to chart some of the best musical performances of all times. A screenplay by Michael Weller + the genius performances from Treat Williams(Berger). For a deeper review : http://www.rottentomatoes.com/m/hair/.