Dave Smith Instruments SYNTHESIZERS

hey,
i'm kind of frustrated right now.  all i want to do is filter some noise with the 4pole 
filter and have it resonate/self-oscillate at the cutoff freq.  Soooo.... i have the noise 
turned up only a little bit (9), the resonance all the way up, they key amount set to 72 
(what it says in the manual to get a semitone relationship)... .and i have made sure 
that oscillator one is in normal settings etc... but I can't get it in tune.  it always 
seems like the intervals are a bit flat.  any recommendations?  I think i've tried 
twiddling with all of the settings mentioned with no luck.  I also have tried messing 
with the audio mod setting on the filter and that seems to change it some, but I 
haven't gotten it right yet.  Just out of curiosity... what exactly is the audio mod 
param on the filter?  Can someone explain that also... thanks.

mark