This is less a concept album than a marketing ploy. It's a collection of previously released Elvis Presley covers (no dates given, but given the sound, which is occasionally mono, going back at least to the mid-'60s) by two great country singers.
Conway Twitty, of course, was originally marketed as a rockabilly artist, so it comes as less of a shock to hear his Elvis impersonation on "Blue Moon." Merle Haggard, who has a bit of the jazz singer in him, doesn't take to this exercise quite as naturally, but he's mostly convincing and his version of "In the Ghetto" in particular is deeply affecting. ELVIS FAVORITES is a mishmash, but fun.