[sdiy] Interesting f vs. t graphs of pitch instability

[David G. Dixon]

> Finally fixed it. It wasn't VR4, it was the CA3140 (IC5).
> Replacing it made the wavering go away.

Andre, I recall our discussion about VCOs vs DCOs and how you thought the
former might sound better than the latter because of slight frequency noise.
It would be interesting to see whether there is any measureable noise now
that the unit is fixed.