I am only familiar with him in the WOODSTOCK film, which we saw a few years ago in a local film festival. Big screen, great print, great sound system, enthusiastic audience.
It amazed me then that Havens with limited guitar playing was bookended by Hendrix, a relative guitar master, and how those two remain pivotal memory points for me about that film. Havens eschewed guitar virtuosity, yet his percussive playing was the ideal support for his singing and 'presence'. Hendrix was at the other end of the spectrum - his guitar was The Huge Factor of his presence.
And yet both remain vivid memories of that film for me. Almost complete opposites but, y'know, it'd have been FUN to see each of them do the vocals on the others' songs. Great fun, in fact. Too bad guest-star duets back then were only used on occasional variety TV shows. (I can only imagine Havens' sandblasting PURPLE HAZE vocals...)
Havens continued to make rounds, too, though I never saw him. I'm glad to see there are more recent YouTube videos of his shows.