vibrato

[Martin Czech]

:::Another approach is to use a phase shifter circuit without the
:::original signal mixed into the phase shift output.  That means you can
:::take a standard phase shifter stomp box, like the ol' MXR Phase 90,
:::and clip one connection, and it's a vibrato.  Note that the effect can
:::be pretty subtle at low sweep speeds.

Yes, this is because a phase shifter alters phase,
and frequency is the deviation of phase.

If phase chnage looks like this:

K+C*sin(wt)

Frequency looks like this:

C*w*cos(wt)

so for low w (modulation frequnency) frequency variation
gets very small...

All intuitive math, not 100% correct interpreted...

This parameter dependency may be a disadvantage of
the phase method.

m.c.