[sdiy] Partial solution - WAS: RE: Odd transistor connection, why???

[JH.]

>The VCO core is still baffling me, but I'm happy to confirm the EG
>operation. Now I can learn more about it.

The expo converter looks a lot like those in the EMS VCS3 (and the Living VCOs, for that matter).
But where EMS have used a reverse-biased NPN in the emitter path of a normally connected PNP to work as reference voltage and servo 
amplifier, *this* circuit seems to marry the two functions in one transistor. Interesting! I would not have expected this to be 
working, but as it obviously does, it's quite brilliant as a low-cost solution, going one step further than EMS.
What I don't understand: The collector of that zener-connected transistor should now work as an emitter, so contrary to what EMS did 
this works as an emitter follower (and zener diode), which would not provide the necessary signal inversion to feed back to the 
emitter of Q7. Strange. But apparently the collector of a NPN with reverse-biased BE doesn't work as expected anymore.

The diode-connected transistor seems to be the discharge path for the integration capacitor. Low leakage, as was mentioned before. 
Q1 and Q2 form the schmitt trigger.
Integration cap is rather small, so they need very low leakage (thus Q5 instead of a diode), and probably get away with a rathe 
rhigh resistance to discharge it (1k2||3k9).

Just som eguesses, of course. Would be interesting to see the whole schemo.

JH.