The earliest I can think of is in the 40s country song "Tennessee Waltz", wherein the singer dances to said waltz with their darling, meets an old friend, and loses their darling to that friend to the beautiful, sad strains of a song about that very subject. Looked at this way, it almost feels like a Buddhist lesson about the folly of attachment and the falseness of the world.
There are a lot of "dance" songs that invoke their own title, propagating theoretically pre-existing crazes such as The Twist, The Madison, The Locomotion, The Electric Slide, etc., but in most cases it's clear that they're referring to the dance, not the song itself. A possible exception is "The Time Warp" from Rocky Horror Picture Show, wherein the Riff remembers not just doing the dance, but also people shouting the lyrics to the song. Then you get Columbia's great middle-8 break that seems to be some sort of origin story for both her current persona and the song itself. Of course, since the song is purposely mind-bending and vaguely about some kind of time travel, this kind of self-referentiality feels a lot more in keeping with the tone than for the beautiful "Tennessee Waltz".
A case with RL chronology behind it is "Boyz-n-the-Hood" from Easy-E's 1988 album Eazy-Duz-It, where in an intro he describes how he blasted an NWA album through his car speakers and then "played my own shit it went something like this," followed by the body of the song. The meta-ness of this is a little compromised by the fact that he had in fact done a shorter version of that song on an NWA album the previous year, so you could almost think of the 1988 version as a second song about listening to the 1987 version. But he commits pretty heavily to the reality of the second part, so even if it's not as reality-warping as the first two it at least suggests the ability of music to take us mentally into the past and perhaps to reflect or induce our tendency to repeat past patterns of behavior.
I feel like I've heard others but those are what I can think of. Anyone?