The Cowsills' cover of Hair. The song was produced by Bill and Bob Cowsill, who were both around 20 at the time. The kids played all the instruments, the drummer (John Cowsill) was only 12 or so. And the video clip is something else.
Really grown to like this a lot over the years. It eschews the obvious heavier riffs in the original but the playing is true to the title of the song courtesy of the intricate solos of Japanese guitarist Michio Kurihara (Ghost, The Stars, White Heaven etc)