MOTM

I just listened to the crow's 485 demo and it's cool, I noticed on 
the last note,a low C (almost b natural actually) that opening the 
cutoff makes the pitch more flat while closing it gets sharper, I 
think this is somewhat a psychoacoustic matter also but I think this 
behaviour was far more evident than in other filters, did I miss 
something? any thoughts?
Enrico (Italy)