If the app work slowly, try to turn off something that you don't need in the video (like texture, saber,...) for better performance. Or try switch to the computer (if you have one).
I think the MIDI an be record at a computer, so you should install the app in your computer. But if you don't have, please wait the response from visualmusicdesign...
Try to record in a different app and then import in the app, because I was explore many issues while recording in SeeMusic