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.