The Music Got Recycled
Yes, it's a weird picture, but I can watch anything from the 60s. I've enjoyed the "Magic Christian" and "Arnold's Wrecking Crew" (maybe that was the 70s).
That said, what struck me the most was the theme. When I heard it in this movie I was sure I had heard it before, and sure enough, 3 years later an instrumental version of Hefti's theme can be heard in Elaine May's masterpiece; "A New Leaf".
If you have seen "Oh Dad", get "A New Leaf" and enjoy it on its own merits, but listen in after the wedding scene when Matthau and May go off on their honeymoon, you'll hear the "Poor Dad" theme while they are riding the golf carts.