[sdiy] weird PNP/NPN expo questions

[Dan Snazelle]

hello there

I am working on a project that right now is using a expo made out of a PNP and an NPN 
(the NPN collector is the output into the VCO)

basically the opamp summer (with tempco, pitch control and expo FM)
 goes into the base of the the PNP. the PNP emitter goes through a 100k into +V and also into the BASE 
of the NPN.

there is also a 220 ohm resistor going grom the collector of the PNP into the -v rail.

the NPN emitter goes to ground and the collector connects to the VCO/lfo

so....my question is this

1. is this setup a curent SINK or a current SOURCE?

2. if i wanted to replace it with a more standard pair, would i use a pnp pair?

3. my main concern is figuring out WHERE or how to hook up a summer for LINEAR FM.

thanks everybody!!