Hi, Nick ! Thanks for asking, since I think many other Basschat members wonder about that.
There are many knobs, and all of them have a function ( on EARTH! Just kidding, Nick, ok? ). So....
From right to left, on the bottom line, the 3 first are : main volume, piezo volume, MIDI volume.
From right to left, on the upper line, the first is pick-ups balance.
So, as you noticed, this piccolo bass has a big electronic system (MIDI, and piezo pick-up) and, for the "regular" pick-ups, the Alembic-style filters systems. For each pick-up, you can select the frequency you like and modify the Q width.
You can check this on the pic I uploaded just for you!
Don't hesitate if you have any question; have a very good day !
Xtof