We could call this a step-analog wah.
But as it is indescribable, it is better to go to:
https://www.zvex.com/effects.html (mp3, video, user manual ...)

UTILIZATION

There's lots of little knobs to turn, it's very funny!
- A mini switch to select between 4, 6 or 8 step per cycle
- 1 knob to select the speed of the cycle
- 1 knob for each step of each operating cycle as a wahwah (but fixed)
- 1 footswitch on / off
- 1 footswitch "back to the beginning of the cycle"

SOUND QUALITY

The possibilities are vast, soft ripple of the cutting type tremolo ground thoroughly.
In any case the sound is fabulous.
One small problem: My OohWah "clipped" when two knobs settings neighbors opposed.
The gap is too large between the two sounds.
There is still an enormous range of possible settings, giving the sounds that were unknown to me until then. In short, it's everything I love.

OVERALL OPINION

I use it on a guitar but I think it will also mix well with an analog synth.
I love Zvex effects, especially those with an "analog sequencer", so I'm satisfied.
In addition, I ask a tap-tempo Cusack Music, to use my OohWah on stage in any circumstances.
Used on ebay States, it's worth.
It's small, it is very expensive but when you love ...
I do not mind one or two!