[otnt]

I'm very afraid this can only work when all members have the same tablets, the same software, and exactly the same settings.

Please see the example showing interaction between iOS and Android: www.youtu.be/H-xTFnFNofc
The important point is to have same file name. Musicians can have a different parts of the same piece (violin 1, violin 2, viola, cello etc.) but the individual parts/files need to be saved with the same file name.

... some may want to turn a full page, others a half-page, page being scrolled...

For serious professional work you would use large (12inch and larger) tablets, 2-in-1, flip devices, monitors and ereaders. No more half-pages or scrolling.

For ChordPro files, I like smaller lyrics and bigger chords, but a singer may want bigger lyrics and maybe no chords at all.

Yes we are discussing apples and oranges. I am interested in sheet music: MobileSheets - The Music Reader. You like ChordPro files and lyrics... Others MIDI, mp3, audio player, backing tracks, metronome, drawing, transposing, automatic scrolling... All that stuff bugging proper sheet music reader.

We could never turn our pages at the same time. Have you even looked at an orchestra? You'll notice that most instrument groups have different scores, hence different moments to turn the page.

I am professional musician with many symphony orchestra, chamber orchestra and string quartet years done. I know there are many concerts with one or max two pages pieces long.
Having two pages (2 screens or one really large) in front there is no need to turn the page.

I doubt whether it will be of sufficient general use to put a lot of effort in.

I am also sheet music producer. There is a huge demand for smaller ensembles sheet music. It's not that difficult to produce multi-page ensemble scores with the same bar number turn to turn at the same time.

Anyway once master/slave feature is enabled on MobileSheets I am happy to make YouTube tutorial.
Bluetooth mesh network standards should be announced soon so it might be easier to implement.