I did, a few years back. I simply used a transistor as a VC switch.
10k resistor to the "base", thats your trigger input....... then the
other two terminals (emitter & collector) become your gate, doesn't
matter what order because it's bi-directional. You can use this to add
voltage control to any switch really, before I added midi to my SK-8,
i used this same method to add trigger inputs for each of the sample
pads 1->4.

good luck

ryan

--- In CasioSK@yahoogroups.com, "placebot2001" <placebot@...> wrote:
>
> hi
> has anyone modified their SK-1 so that the one-key-play can be
> triggered by a trig out from drum machines, like a Roland TR-707? i've
> heard of people using a 5v reed switch or optocoupler. anyone know
> what works best?
> -Scott Campbell
>