Blue dog, I can't tell you the artist, because very seldom did any group perform this song the same way twice, and here the words are edited out, so all you've got are the solos. It's definitely St. James Infirmary.
The choreo was by Shanti Ruspaul AFAIR, so the music could have been from anywhere. St James Infirmary is an old, old piece and everyone's done it.