Jim and Big Al's comments reminded me of this -- recently, a Mudcat thread came up (link) looking for info on an obscure old Pete Seeger song. Looking for leads, I listened to a few radio shows of his archived from the late 1960s. During one radiothon, he was playing to raise money for a local station when a listener called in and asked him to play Here's to Cheese. The song is long to begin with (the linked version is 6-1/2 minutes), but he went on with it for probably 15 minutes on the show. I could not wait for it to be over with, mostly because 80% of the song is a repetitive chorus. He says it's a variation of Froggy Went A-Courtin written by an English farmer friend.

Pete Seeger Marathon II WBAI 1969-05-10 -- for the curious, that's the radio show I mentioned, and his story and singing of it is buried somewhere in that show (both the original request, when he demurs because he can't remember how it starts, and the eventual elongated performance of the song).