So I read a cool article about teaching choirs to sing in parts, which helped guide me on the things someone might need to work on when starting out in multi-part voice music. The simplest part songs were rounds and partner songs (basically, potential mashup songs) and it got me going on how I might structure a track so as to be useful for someone on at least two different levels of learning, so that one recording can be used by the same person to learn multiple things:
I am yet to figure out a plausible way of teaching two parts simultaneously. Stay tuned!