to Michelle (05 sep 10) -Just saw your post now...sorry! Re : Ridin' on a Humpback Mule...I know of a 1935 recording of this (your lyrics are very close) by the Shelton Brothers. The link below should take you to a little player from the website jazz-on-line.com which will play the song. The website itself while being mostly jazz has tons of old-time music too!

http://incoming.jazz-on-line.com/a/mp3o/DEC60263.mp3

Enjoy!