I'm using the iPad Pro (12.9") also, with the unrealBook app. I don't need to play tracks, so I use it for music (PDF file) display with the musician's music display app 'unrealBook' which has worked well. This app does have music player features, but I don't use them so I can't report on how well they work etc.

I also use wireless MIDI from the iPad to my Genos, to recall registrations (I've written about that in other threads), plus AirTurn units for page-turning. I network with up to 4 other iPads in band/jam/party situations also, so that they all display the same music that I show on my 'master' iPad (this is a function within unrealBook).

Jim