A slightly peculiar thing, this. When Gregg Allman's death was announced recently, there was some reference to this album in passing, and I assumed then that "Gregg Allman and Woman" was album title rather than artist name. I do remember the unlikely couple (in both musical and artistic terms) appearing on "the Old Grey Whistle Test" to promote it at the time of release.
I could maybe understand the billing (if only in 1977 terms) if they'd been on labels with no commercial relation whatsoever, but the strange thing is that Warner Bros was Cher's label (Capricorn was only distributed by Warner brothers) but the album appeared with only the Allman name quoted. Couldn't happen today....
Maybe if Taylor Swift and Tom Hiddlestone's brief personal relationship had extended into a musical collaboration, performing a song previously recorded by Hank and Audrey Williams, the billing for "The Pale Horse And His Rider" could have been "Taylor Swift and Man".