In a Doc Watson music book I have, this song is titled 'Settin' On Top Of The World'. It was originally done by the Mississippi Sheiks and has been covered by many people, including the Grateful Dead.
Doc commented that 'I fashioned my arrangements from Frank Hutchinson's The Train That Carried My Girl From Town and Worried Blues; I just worked out a finger-picking version in an open tuning'. (It is open D tuning, capo first fret).
If you don't know Doc, consider finding his songs. He is a formidable finger-picker and flat picker, he sings, and plays other instruments such as banjo, blues harp, and mandolin.
For a truly remarkable essay on meeting Doc, seeing him play live in later life, and how he interacts with other musicians, read the following article; it is fantastic:
ekhornbeck.blogspot.com/2005/1...
I have done a slideshow video featuring mostly early images of Doc and other bits and pieces, around the same period as this song.
Update: Sadly, Doc Watson died on 29 May 2012 following surgery, at the age of 89. R.I.P. Doc. (There were 80,107 views as of 30 May 2012. Prior to Doc's death, this slideshow video received around two and a half thousand hits per month since it was put up in Nov 2009 . In the two days following his death, there were 13,000 hits).
Comments are invited.