On this date in 1969, The 5th Dimension's cover of "Aquarius/Let The Sun Shine In" – one of several songs that charted from the musical "Hair" – began a six-week run at the top of the singles chart.
It's a longer story than you're going to get here, but the short version is our garage band once got drafted to be the rhythm section to accompany our high school band and choir on this medley, and I can tell you from personal experience that the bass line on this is great fun. I'd do it again tomorrow if someone offered me the chance, and I'd probably only need one run-through to have it down after all this time.
And yes, in the video clips from the 1979 film version, directed by Milos Forman and choreographed by Twyla Tharp, that is John Savage (who'd just come off of "The Dear Hunter"), and that is Treat Williams, and that is in fact Beverly "Ellen Griswold" D'Angelo. And I'm pretty sure there's a quick glimpse of Nell Carter in there, too. Don't sit there gaping. Go watch it. Yes, of course it's dated. In fact, the 1979 film itself was already some distance from the 1968 stage musical. Why is this necessarily a deal-killer? If it was an exact and precise depiction of the way things are today, what would be the point?