Hi,
I like your idea.

I can't recommend a specific product, but I would find something with a 12" screen size to be more suitable for the general public - considering accessibility for people with below-average vision.

Note that if you are going to go for 10.4", it will be cheaper to buy a tablet compared to buying a just touch screen monitor with the same image quality - so you might consider that (but it would probably be harder to set up and more error-prone).

I'm actually thinking of donating a spare 15.6" display from the organ build as I've had to go native physical stops due to poor accessibility with a linux system and ORCA with Touch UI. so the display that's spare would benefit the church build better than it sitting doing nothing. just trying to think of mounting the pi to the rear, probably vesa mount it.

I can't recommend a specific product, but I would find something with a 12" screen size to be more suitable for the general public - considering accessibility for people with below-average vision.

Note that if you are going to go for 10.4", it will be cheaper to buy a tablet compared to buying a just touch screen monitor with the same image quality - so you might consider that (but it would probably be harder to set up and more error-prone).

I posted some time back about a plan for building a replacement digital piano for my local church. That got delayed due to a few things and they've had to make do with the organ installed which is having some small issues and I can't get there to resolve it until COVID19  clears down. I'm in a high risk area so it is a bit of a swine.

Now that I've fallen for the raspberry pi 4B and have to admit I wish I'd taken this on sooner, I'm using this in developing my own speaking digital church organ, yes, a 4 manual stunner, I started re-examining the build for a digital piano for the church's needs.

So, I'm willing to donate a spare license of my Pianoteq 7 Studio setup to our church, yes that leaves me 2 licenses  left.

What I'd like to achieve is a touch screen based setup, running Raspberry Pi OS, Pianoteq in kiosk mode ideally so no other use can be undertaken and so that the software boots as priority.

Could anyone advise me of a suitable size touch screen that most people could get away with using, in order to navigate and adjust parameters of the software? I had thought something like a 10.4" or similar, remembering the days of older touchscreen workstations like the korg triton, OASYS,, etc

the plan would be to use the touch screen as the primary UI with the Pi4B attached behind and a Hifiberry DAC2Pro or DAC2Pro XLR sent out to an amp driver, etc.

Any opinions would be a huge help here.

lew