New World Records
New World Records is a label "dedicated to the documentation of American music that is largely ignored by the commercial recording companies."
Based in New York, the company was founded in 1975 with funding from The Rockefeller Foundation"with a mandate to produce a 100-disc anthology of American music encompassing the broadest possible spectrum of musical genres." About
It has a small but significant set of American traditional music titles which can be viewed Here.
They can be sourced in the UK via RSK