I think it would be useful for learning, to be able to record songs playing, to later accompany them with the crank while they play, or accompany playing with a string.
There’s no persistent memory to work with. EEPROM is not meant to be used too often and has limited read/write cycles and even if it didn’t, it’s not enough space: 4kb total! I could hold some in memory, but they couldn’t be saved.
I don’t know how to record songs :-). The logical thing would be to record it as MIDI… I’d have to learn to do that, if that’s something that can be done on a teensy in real-ish time.
In my opinion recording makes more sense on the synthesizer-end (whatever’s powering your speakers), where you have control over what you attach it to and much better software and hardware to work with (a tablet or computer).
I think it would be useful for learning, to be able to record songs playing, to later accompany them with the crank while they play, or accompany playing with a string.