The block-diagram level breakdown of the different sections of silicon is really a wonderfully helpful way to look at this. It makes the zoomed in view of each section more meaningful. Then seeing the die photo of individual transistors or groups of them, next to schematic level interpretation, really drives it home. Thanks for making something so instructive.
Have you decapped other sound-making devices? The greeting card chip makes me think of the ubiquitous "laser noise" chip from countless 80's kids toys. That or one of the many kid's keyboards or baby noise console devices, that have all of the function inside a single epoxy-blobbed die. It would be pretty fascinating to see a similar breakdown of which sections encode samples, note values, rhythm and sequences, control inputs, etc.
Your description immediately made me think of the TI SN76577 "Complex Sound Generator" IC [1]. If I'm not mistaken it was used in the early versions of the MB Games Electronic Battleship game (think falling missile and white-noise explosion sounds).
Edit: Not a decap, but this page [2] has links to the datasheet and other reference material that includes a block diagram, and even has circuit diagrams of the internal circuitry.
Edit 2: A video [3] demonstrating some of the possible sounds.
Have you decapped other sound-making devices? The greeting card chip makes me think of the ubiquitous "laser noise" chip from countless 80's kids toys. That or one of the many kid's keyboards or baby noise console devices, that have all of the function inside a single epoxy-blobbed die. It would be pretty fascinating to see a similar breakdown of which sections encode samples, note values, rhythm and sequences, control inputs, etc.