UI space.. few ideas..
And it just came to me, why not make it similar to audio synth app, Ableton in this case (pic in attachment)
Idea is simple, when you run out space in the instrument rack, it will start stacking to a point when you just click and drag, so you can add as much instruments as you like.
Please discuss
P.S.
why not make sliders rotary? takes up a lot less space and looks cool