[sdiy] breath controller input

[Rude 66]

my latest project is the hacking up of a yamaha ds-55 (budget 4 op fm synth)
with a broken keyboard, to make it a suitcase synth. i've fitted the main
board in the case, cut out the in and outputs in the wood, and made a top
'panel' that holds the display and section for the programming knobs.
actually a surprisingly easy job, and all done in one day. it'll be like a
midi module.
after i cut out some room for the pitch/mod wheel section, there's quite an
empty section left on the front panel, and i was thinking of adding some
alternate kind of controls for it.

the ds55 itself is not very programmable (but it'll accept other 4 op
soundbanks via midi) so something like a midi controller box with knobs or
faders doesn't do very much. then i remembered it has a breath controller
input. i found all kinds of online info on how to build wind controllers,
etc, but not much on what else you can plug into that input.

what does it take? a voltage? i'm thinking of adding something like a
joystick, photo resistor, speak & spell keyboard, ribbon controller, etc.
would that be possible?

thanks as usual!!

r./