Anoter way to gauge the contribution of A. P. Carter (Alvin Pleasant Delaney Carter) is the enduring popularity of his arrangements.
BMI lists 277 titles under copyright with A. P.'s name. I suppose Peer Music holds most of them. The fact that Peer got the Carters started in recording is covered, but nothing was said about the current status of the man or his company. The little compamy started by Ralph Peer (died 1960) maintained its independence and now has a 300,000 song catalogue and operates in 27 countries. One of their websites, digitalpressure.com, offers direct downloads of master recordings. Six songs in "O Brother, Where ..." bear early Peer copyrights. Ralph Peer II is currently in charge of the company.

Data at BMI and www.peermusic.com. The latter site has interesting notes on company history, and a page on the history of the Carter Family.
Peer Music