Ideas for a keyboard module

Hi community

A few years ago i found an AKAI synthstation25 keyboard somewhere in the trash.
I never expected that i will find a use for this but recently i tried to create an eurorack module with it's keyboard.
Within a few hours i successfully built a fully functional eurorack keyboard on the breadboard with:
- 1 output jack for CV pitch
- 1 output jack for CV gate with LED indication
- pitch bend potentiometer +/- 1 octave
- another potentiometer for +/- 2 octave shift
- beeing a class compliant midi controller as well (polyphonic for possible usage with hermod's usb host jack)

Next thing i am going to do is creating a prototype PCB and a frontplate (~50 HP)

But before that i should have finished my decision which functionality will be included in the final product.
there is some space left on the frontplate (~15 mm x ~150 mm) where i could add controls for any further features (jacks, potentiometers, leds, switches).

I dont want to build a feature packed keyboard (like keystep). i just want to use the remainig space for something useful.
Currently i have no clock + reset input so "sequential/arpy" features should be avoided

Does anyone have an idea which functionality would make sense?

my ideas:

Vibrato

for low frequency oscillating around the current note pitch
no additional jacks needed
- 1 potentiometer for speed/lfo frequency
- 1 potentiometer for amplitude

Hold

for keeping the gate open until the next note hit
no additional jacks needed
- 1 LED switch

EDITED Jul 8th 2022, 06:07

Vibrato...if it had an aftertouch sensor. I don't think that keyboard does, though. Therefore, the "hold" makes more sense; I would check how the ARP 2600's "keyboard latch" function works, and then proceed from there. You might consider mounting a 1/4" jack for a momentary-on pedal for this, too.

@Lugia thank you so much for your suggestion!

I am sure there are no aftertouch nor velocity sensors on the keyboard unit. just a switch matrix where you can track keyDown and keyUp of each key.
The "keyboard latch" looks interesting! but having an additional CV pitch out jack i could make a polyphonic CV keyboard which seems to be not that easy.
But i will give it a try (at least on the breadboard).

I also like your pedal idea! i didn't think of that.

Yesterday i started to create the frontplate for the keyboard unit. Due to some plastic structures of the original housing there is less space left than i thought before.

Anyway - thank you!!!

Yeah, the pedal I'm sort of envisioning there is something akin to the "sustain" that I've got on the JP-6 and/or CS-80 here. Sort of a "latch" to hold a note so that you can have both hands free for going bonkers on the controls. This REALLY is a godsend with the CS, I should note...as there's a lot of sonic fun to be had while you're tweaking the sounds on the "tabs" while going totally off with the ribbon. It also lets me lock in arpeggiator pitches on the JP during live performance...very Berlin School-ish results there. But even with a monophonic synth, that one function has loads of wonderful "abuse potential"!

i finally have finished the frontplate and the prototype PCB.
Now i have clock+reset inputs on the backside of the module which would really open tons of feature possibillities but unfortunately there is no room for additional jacks or controls. And there is no analog or digital pin left on the Arduino UNO as well. I already replaced multiple led pins with an adressable LED strip which only needs a single pin on the Arduino for using 36 RGB leds.

Anyway - i am glad that i was able the create a perfectly working module that absolutely meets my requirement of having a tiny keyboard in the horizontal row of my rack. And i really like the vibrato feature (or the fact that there are no additional modules needed to create such vibratos).

https://www.modulargrid.net/e/other-unknown-akai-synth-station-25-mod