Boss OC-3 advice

[garyt]

I have an OC-3 and am trying to use it to create some synth type sounds.  I am getting some good sounds out of it, but every now and again I'll get some random overtones, almost like the pedal is squealing out some random notes.

Does anyone have any good tips when using the OC-3 or any decent settings?

So far, the best I can come up with is:

try and avoid having 2 notes ringing.  It seems to work best if I play on one string only, but that can't be right.

Oct 2 mode:.  12oclock, 12oclock, off

Poly: 12oclock, 12oclock, on full,

Drive: work in progress 

[Stub Mandrel]

I haven't used one of these, but by definition it's only polyphonic in poly mode.