I ended up focusing on putting other songs into their own PICO-8 carts. I'd really like it if I could decide to try this with a song that doesn't use triplets, because I think it would be easier if I could end playback early somehow. Wait... if the desired measure length is a multiple of 32 ticks (and it is, as a matter of fact), then I can set it to loop at a later point, and have another track that actually handles the termination, by being the desired length. This will require some weird sfx loops, but it was always going to. I should really be writing this stuff down.
I'm going to try to get to bed earlier, and read a bit in bed, but we'll see.
We recently watched The Apple, and it is too late at night for me to do that movie justice. Brief remarks: if you like Shock Treatment, it's worth checking out The Apple, but I prefer Shock Treatment for various reasons, such as that its jokes actually land.
ANyway, bed, getting there, yes, good night.