Hair: Original Broadway Cast Recording (1968)
I tend to prefer the original Broadway recording over the film's updated, better-produced soundtrack, which sands off some of the rougher edges, though the film versions do have a more radio-friendly pop veneer that makes many of them work as legitimately solid Adult Pop tunes even stripped of the play/movie context.
Everyone (I assume) is familiar with the "hits" from the album, the opening anthem "Aquarius" and the timeless piece of sunshine pop "Good Morning Starshine" and closing opus "The Flesh Failures (Let The Sunshine In)." But the thing is truly loaded with catchy little ditties, most checking in at just a minute or two before moving on, delivering their hook and heading to the next bit. "Donna" and "Manchester England" and "I Got Life" and the title track are all fun sing-alongs; "Air" and "Initials" cute abbreviated bits; the ballad "Easy To Be Hard" is surprisingly solid soul/pop (later covered by supergroup Golden Smog); "Frank Mills" is a charming earworm (later covered by the Lemonheads); and "Walking In Space" and "Be-In" are convincing psychedelia. Plus the delight of the frank sex romp "Sodomy" and the confrontational "Colored Spade," songs that shocked little 12-year-old me and sent me running to the dictionary.
I assume this wouldn't hold up well for anyone not familiar with the play or the film ("Aquarius," "Starshine," and "Sunshine" aside), but I still find it a fascinating and enchanting bit of history, with far more original pop hooks than most show-tune collections with which I'm familiar.
Here are the opening/closing tracks from a Broadway revival, as performed on Letterman: