Ray Charles' Modern Sounds In Country and Western Music (two volumes) are timeless masterpieces. I imagine their success was a significant part of what led many soul/jazz/R&B people to record country music. But I'm sure a big part of the reason was how great, in fact, so many of the classic country songs actually are. In terms of the songs themselves, I see a lot of commonality between classic country and classic soul/R&B repertoire. Personally, I view them as different sides of the same coin.
You're right, Dave. A humorous quote from the back of an album comes to mind regarding the melding of Soul and Country & Western. This is from the LP "Sounds of Doug Jernigan and Gary Adams";
"Country and Western has for a long time shared an affinity with 'Soul' or 'Black' music and an ever increasing number of black artists are being attracted to 'C' and 'W' as attested by one; Charlie Pride. It is my opinion that the reason for this attraction is the feeling which is the basis of Country Music or any music that generates emotion. The feeling is called 'Soul', and music without it is flavorless.
The production of this album combines these two vital musics and the fire of these seasoned musicians, three white and two black, into some highly enjoyable and interesting listening.
During the 'session' bassist Larry Randolph quipped with a remark which broke everyone up, including yours truly. 'If this is Country and Western, you can call me a SOULBILLY!!! As for Gary and Doug, call them hillbillies if you like. They don't mind, because they can play" - DON HALES.