In 2003, thirty years after he settled in North Carolina, Erbsen published Rural Roots of Bluegrass: Songs, Stories and History and this was his conclusion about the roots of such music:
It was clearly the Scots-Irish immigrants who contributed most to what would be called Appalachian or old-time music. [Rural Roots of Bluegrass p 126]
Today some people say that it was the Irish who contributed most to Appalachian music and yes it was people who came from Ireland but they were Scotch-Irish, the descendants of the Ulster-Scots who crossed the Atlantic in search of a new life in a new land.
The book is available for purchase on the internet, along with a CD containing 14 songs from the book, and it is a great source of information about many traditional songs. In 2006 Erbsen also published The Bluegrass Gospel Songbook, with more than 100 favourite gospel songs.