> Retro Song Bird has a map of 1900+ carts and knows which sections of the ROM to read.

Huh. Was assuming that this was just Tonies for Game Boy enthusiasts, but seems it actually reads the songs from the cartridge. Not bad!

I'm getting inundated with Tonies ads now haha. I wish I could just use NFC and play pre-canned audio, unfortunately for me, the rights-holders might take issue! I'm also targeting musicians, so synthesizing the music is pretty powerful. I can do tempo control for beat matching of two carts, as well as split out the stems (e.g. drums, chorus) from the 4 instruments the Game Boy uses so a DAW can control and remix the tracks.