[sdiy] Unstability of oscillators and psychoacoustic qualities

[jhaible]

> I'll suggest that the most typical cause of "coldness" in an
> oscillator is an unnatural synchronization.
>
> A classic example would the be Top Octave Generator chips that keep
> the pitches in a synchronization with each other that you just don't
> find in nature.  Or any divide-by-N situation for that matter.

I fully agree.

But as you mention it, even such situation can eventually turn into
something positive:

The Korg Lambda has 3 HF-VCOs and 3 sets of divider circuits
(for the strings sounds), and 2 detune pots.
Now these are probably the *worst* interlocking VCOs I've ever seen.
(If you adjust the detune pots you will really hear and see the VCOs
"jump" to the same frequency - "see" is because there are LEDs
that indicate the beat rates.)

But not comes the trick. A modulation circuit (I think it's a 3-phase LFO)
kicks the HF-VCOs out-of-lock periodically. (If your initial
detune setting is close enough.) And *that* gives the most wonderful
string chorus sound. (I would rather call it "lush" than "warm", but
these are just words anyway.)

JH.