synth user interface

ok so i've been thinking about how the buttons should work on the synth, and i'm starting to diverge a bit from the initial design. iterate perhaps.

L/R shoulder buttons in particular need to be careful with sustain. if i press and hold R to get into the next octave up, then press a bunch of notes, i probably don't want those notes to be all sustained; i.e., i probably am just doing a solo up in the next octave. what we probably want is holding both L+R will ensure that any currently held notes become sustained, holding either L or R will ensure any already-sustained notes stay sustained. e.g., hold L, press and hold C (plays e.g. C3), press and release D (plays D3), hold R, release C (continues playing C3), release L (continues playing C3), press and release E (plays E5), hold G (plays G5), hold L (continues playing C3 and now sustains G5). i'll have to try it out and see what feels intuitive but i think that's closer to something that will feel right.

speaking of octaves, it'd be nice to have a visual indicator of which octave you're in; i'm thinking an LED here. the KORG microKey does something like this and it works ok.

the joystick i think i will bring back, but i want to make sure users can choose what modulation they want on vertical and horizontal axes. i'm thinking of having two indicators for this, e.g., two LEDs, one for each axis, and two buttons to change what each axis is. (i might be able to get away with just one button; holding it down and then pressing in a direction will change that axis modifier to something different). these might be some of the available options:

• pitch bend - fairly self explanatory, pressing left (if on horizontal axis or down if on vertical axis) will bend pitch down towards the next flat, right (or up on vertical axis) will bend pitch up to the next sharp
• waveform - with three options (sine, triangle, square), you can go up (or left) to modulate into the previous one, or go down (or right) to modulate to the next one. the waveform will be a linear combination of the two.
• vibrato amplitude - oscillating your pitch doesn't have a good "positive/negative" counterpart, but "volume" vibrato might work nice in the opposite direction
• vibrato frequency - how fast your vibrato acts. might also be nice to have a volume vibrato frequency.
• duty delta or bit crush - changes the timbre and distortion of the wave
• volume - i know, this might be redundant if i have a potentiometer on the back for volume. but could potentially remove the back volume if this works well.

however, in case you want to play with both hands after finding a cool setting, it'd be great to have a "freeze" option. i'm looking at a joystick with a button, which i think could work. but then it's a question of do you need to press the button again to start accepting changes again? could be cool to freeze at one value, then swing to the opposite and unfreeze.