Odd tonight I heard music on 640 alternating with the Oklahoma City station. Moving the radio got the music, which was Birthday by The Beatles and some Lennon-led Beatles tunes.
Then it faded and only Oklahoma was received.
Tried to match with other stations in LA (running talk online), Iowa, Ill., New Orleans, Memphis, Florida, but no luck.
May have been KYUK in Alaska, as online it shows a program called Rick's Rock is airing. But when I heard the song it was playing, could not hear the AM enough to detect the song.
Couldn't find any other station with a rock music format that would match it.
UPDATE: Listening about an hour later, the music is coming through, but it sounds Spanish.