My mother described seeing him in concert when he was young. She practically drooled as she described his unbuttoned shirt with his chest on display. (I don’t blame her. I’ve seen Carmen Jones and he had a BOD.)
Anyway, I’ll always love him best for the Muppet Show appearance (which I watched last night in his honor), but this is the first place I ever heard his voice….this duet with Marlo Thomas on the Free To Be You And Me album. The album was born only weeks after I was, but I think I was three or four when I first heard it, in our family room with the shag carpeting and dark wood paneling. 
(Something I noticed even as a little kid…at the tail-end, you can hear Marlo squeak “yay!” and Harry chuckle a bit.)