Hello! I think a really great feature would be to be able to work on 2 or more different midi files (each one having its own visual parameters like particles, colours, size, etc...) so we can render them together like on the image below (it's me playing, I had to "cheat" a bit to have this rendering and it was really long and tough to do).
This feature would induce a "layers" system where each file would have a certain layer that the editor can choose (to be able to see the first layer as the second one is behind : on the image, the rectangles are on the first layer and the comets on the second one as we see the rectangles going above the comets).
With this, it would be also convenient to be able to choose the transparency of each layer.
In case a "layer" system can't be implemented, it would be at least good to have a "colour mixing" system. For example : midiFile1 has a C3 with red colour and midiFile2 has, at the same time, the same C3 but with blue colour. The result would be a C3 with purple colour.
As I'm interested in rendering symphonies, concertos, chamber music, etc... with your software, this feature would be very appreciated and I'm sure I'm not alone in this case.
Thank you for your hard work and your beautiful software!