Yes, programming for playable percussion is very difficult. We need rules that can do several complicated things:
1. Play repeated notes without notating additional notes (i.e. program measured/unmeasured tremolos)
2. Play notes alternatively/randomly (in this case, at different octaves to emulate the left and right hits of a roll)
As far as I know, adequate programming for a tremolo roll in the GPO library is, at this time, not possible.
I've made several requests for additional rule programming options to meet these requirements (as well as a few other requirements needed for other instruments and support for other libraries):
viewtopic.php?f=19&t=1331viewtopic.php?f=16&t=1260viewtopic.php?f=16&t=1259viewtopic.php?f=2&t=1258As you can see, I haven't received any feedback from the forum or the Notion folks. I think we could get much better playback results from GPO (and other libraries that use similar sample layouts) if we have solutions/workarounds to these requests/questions or if Notion could implement some of these features into the rules syntax.