I’ve played a fair bit with MPE in Rack, using an iPad with GeoShred Control as an MPE controller, and I’ve found that it works well. That app works a lot like a Linnstrument, and something like the Sensei Morph in a certain configuration I think, though it has no pressure sensitivity on iPad. There are endless ways to map extra dimensions of expression in Rack, which I find very inspiring!
I did have occasional issues with stuck notes among other things, but I believe they were all caused by either GeoShred (which has been updated since I last used it and I believe multiple issues were fixed), the WiFi MIDI connection I was using, or some combination of the two.
I made a thread with details on how to get that specific setup working. I need to pull out the iPad again and play with it some more so that I can update that guide as to what bugs have been fixed, but I’ve been distracted by other things recently.
I made a version of the MIDI-CV module (called Duo MIDI-CV) which adds additional MPE modes (Rotate, Reuse, and Reset). It also adds a dedicated “Bent Pitch” output combining MIDI-CV’s V/Oct and Pitch Bend outputs, which I found particularly useful with MPE. I should get that cleaned up (in particular I want to widen the display so it doesn’t look quite so awkward) and get it submitted to the library.
Not so relevant for the Morph but maybe worth mentioning specifically for the Haken Continuum and the upcoming Osmose, there’s the MIDIpolyMPE module from moDllz (and my expansion of that module called Super MIDI 64) which supports Haken’s unique MPE+.
I have an Osmose on preorder, so if all goes according to plan in a few months I’ll be playing with MPE in Rack a whole lot more.