Cyrille, that doesn't address my question and you're basically asking me to build a full DAW inside iReal Pro.
Let's be realistic and keep to the scope of this app which is to easily make simple backing tracks for you to practice over,
while at the same time keeping the app simple to use without a million options which would ruin the app for the majority of the users.
If your arrangements need that much more detail you're probably better off building them in Logic.

In this thread I'm trying to figure out how to deal with drum breaks.