I had no idea this was a specialised IC that played this tune! I assumed it was a jellybean microcontroller, but thinking about it it makes a lot of sense. These must have been produced in the literal billions over the past few decades.

For what it's worth, I've come across at least three variants of this particular chip that play slightly different versions of the Jingle Bells/Santa Claus is Coming to Town/We Wish You a Merry Christmas tune. In addition to the one in the video, there's one that holds a note for slightly too long during Jingle Bells ("oh what fun it is to ride" becomes "oh what fun it is - -", and another that repeats the first line of "We Wish You A Merry Christmas" a third time.

I wonder if they're knockoffs, and if so how they're constructed!