Well I had intended to try doing something different this week.
So technically I succeeded.
It's solo piano again, but I had to teach my left hand how to play this somewhat syncopated bass line, before I could actually compose against it.
The 80 bpm tempo was set when I was still trying to learn the coordination (granted, I could've split it out and recorded the hands separately, but I didn't want to). But the more I played it, the better I got, and then the 80 bpm felt way too slow.
So basically, the overall rhythm ended up being somewhat uneven because I was too slow for some of the takes, and too fast in others.
So along these lines, if anyone can recommend a good resource for a songwriter who wants to learn piano, let me know. I already flunked out of traditional piano lessons (heed my advice - don't take instrument lessons as a for-credit class). I guess I'm basically looking for something that can teach me a bunch of left hand patterns that are good for improvisation.