The older recordings are not encoded with the Arbitron type artifacts. New ones may be.
When I compare new vs old, this comes up.
Broadcasters put data in band and have done so for what? A decade now? You mentioned out of band tracking data. I am saying there is also in band data.
Sorry to be unclear.
It is perceptually encoded to ride along with the audio and intended to be inaudible. And it largely is!
It is in band so that AD targeting can be done anywhere audio is played aloud. Say a radio station plays the old tune. It adds its signature to the audio stream which can then be picked up by someone using a tracking device at the local fair, for example.
Adding it to the tunes themselves can do the same for someone using a boom box or some speaker and give some sense of play outside streaming counts, like where exactly are those streams being heard? Your local coffee place might be a likely candidate.
I know the part about radio adding the artifacts is real and old news now. Pretty much all broadcast audio contains it.
The artifacts I hear on some remasters sound a whole lot like those I began hearing on broadcast audio. And back then, I asked and was told nicely how it all worked. Pretty clever tech actually.
I cannot always hear it. Usually, it has to be material I know well and have heard sans encoding. Or, a voice I know well from a time before encoding. It is just different enough to notice for me and some others I have talked with.