As someone who used an ipad for sheet music, its definitely super nice, especially with the apple pencil for wuick markups. I’m extremely disorganized so having all of my music in one app was a ligesaver multiple times

Because the z axis is represented as an extension of the xy-plane, coming out of the paper essentially, so we represent it as up

That’s not true though. While there isn’t a standard, convention is to have z up in mathematics, as z is extending the xy plane we normally work with into a third space.