Taking another look at the schematic (I don't have my oscilloscope right now, so I can't just go measure things to answer my own question), I think that I now see that Pin 7 (ie, the output) of IC16 might be a square wave.
Can anyone confirm (either through analysis or through measurement) that this is true? At Pin 7, does it swing +/- 5V, or +/- 15V, or something else? ...I can't see where the power supply pins for IC16 are defined...
If this is a square wave at this location, I'd need to grab that signal, scale it with a voltage divider to get it the right amplitude for IC21, and then inject it into Pin 3 of IC21. If I want a square wave MG, I'd inject this signal instead of the triangle wave coming down from R26. That doesn't seem too hard to implement. Cool.
The main trick is figuring out where to put a switch for this!
Chip
--- In PolySix@yahoogroups.com, "backshall1" <backshall1@...> wrote:
>
> There's definitely a square wave there already on the LFO. I can't remember
> exactly where, but I know I've seen it on the scope. I've got too many other
> projects in pieces on the bench right now to pull out a Polysix and open it
> up, sorry.
>
> Don B.
>
>