[sdiy] Tune VCO

[Scott]

Am I doing something wrong, or is it really difficult to tune a VCO? 
On several occasions now, I have tried to tune my VCO's, and I spend
hours doing it, and always give up and settle for "good enough". (about
3 or 4 octaves are playable)
Now I'm trying to use several VCO's together, and it's not working out.
I need to get them in tune. 

I've gone from one end of the trimmer to the other, and just can't get
it. 
Right now I'm trying to tune my CGS vco.  I've got 25 turn trimmers on
it.  How much adjustment should I be making?  Should I be noticing
changes with a small turn, or do you need to twist the things around a
couple of times to notice a change?
Also, where does the trimmer usually end up?  Towards the middle, or to
the end of the range?
I've tried tuning by ear, using an analog modeling synth for reference,
and I've tried w/ an electronic tuner.
It's driving me crazy!  I think I've been listening to a constant saw
wave for way too long tonight.  There's still a buzzing in my ears.