Designing a control interface is arguably the most crititcal part when you develope a product. This may be especially true when designing instruments, with which you want to dive into sonic worlds and be in flow with the music. There is nothing more distracting if you have to think too much to achieve a certain effect. Thats why musicians have to practise so much.

With traditional instruments, you once get a hopefully good quality instrument and the rest is up to you practising. Electronic instruments on the other hand are so diverse, every synth or drumbox is different and you have to learn their worklfow like a new instrument. With modular synthesizers it's even worse as your setup is constantly changing.

In my experience, the are to main aspects when it comes to design a control interface, which are quite hard to reconcile: flexebility and ease of use.

The last interface I designed was quite flexible but fiddly to use, keeping me away from using the full potential of the instrument.

As for the ElektroCaster I find It particulary difficult, because there are so many things I wanna do with this and there also many things I potentially haven't think of yet. As the ElektroCaster is the first of it's kind, ther're isn't a real rolemodel I can lean on to. 

Here are some things which sould or could be controllable. You can ask yourself if those parameters should be editible for each string or all strings at once:

-Volume and tone (eq)

-The Sequencer (Number of steps, Speed,...)

-Effects (which effects to use, in which order, the individual parameters)

-Other modulation sources than the Sequencer and what they are modulating         (arpeggiator, footpedals, fader, pressure sensors,...)

Basically, there are three interfacing concepts I'm considering:

1) The full fledged physical interface where the whole top plate is crowded with buttons, faders, displays and all that stuff.

2) The fretboard-centric interface which uses the led-sensing function to edit everything, only accompanied whith some shift (foot-)buttons or switches to select different editmodes. Drawback here is that you can't edit while playing.

3) The app-driven interface where all the editing is happening on a tablet, which sends the parameters vial OSC to the guitar.

Those are the basic routes and and I'm still hesitating which one to take.