[greenlava]

how about a chromebook or a chromebit?  I use a chromebook that folds flat, and it's got a USB-C port where I can plug in an external monitor (and get power, video, and touch over the same wire).  It runs mobilesheets (from the play store) really fast, has active pen input, and the battery lasts forever.  I got a 12" screen, but larger screens are available OR you can just use the external monitor as your primary and choose whatever size you want.  It's a really nice option.

Sounds interesting, but to get a two sheet side-by-side view with 20+" for a sensible cost frame only the chrome bit solutions seems to be persuasive.

I'll forward the suggestion to my music partner!

Thanks for sharing,
Petra

Just make sure you get something that has access to Android apps and the Google play store.  Good luck!