Nerdy record question re George Young and Rufus Thomas sharing a backing track

[mrfinewine]

Rufus Thomas, Funky Mississippi
vs.
George Young and the Youngsters, Sayin' Somethin'

These seem to have the same backing track. How? Why? Rufus's record has vocals; George's is an instrumental. Rufus's is a Stax record; George's came out on a Detroit label, Pacesetter [[and also apparently got a French release on Columbia). George Young was a guitar player, but there's a lead saxophone on "Sayin' Somethin'" that's not on the Stax recording....I'm curious about how this came about. I know, of course, that lots of Detroit backing tracks got reused...but a Stax backing track?? Who's actually playing on it?

Here's Rufus: http://www.youtube.com/watch?v=KmjLmL9OCR0

I played the George Young recently on the radio August 13; it starts around 29:16: http://wfmu.org/playlists/shows/36911

Thanks for any information or insight you may have!!

[mrfinewine]

And, I should add, the George Young single says it was recorded at Pampa Studios. Which I have a hard time believing Stax would use [[United Sound, sure, but Pampa?). So what's the deal here?