I have been wondering about this for such a long time --

There is a certain effect I hear in several Goa songs; if you skip ahead to 5:10, there is an example here.

What I'm talking about is the electronic buzz that goes,

dzoooat! dzaaaat! dzot! dzeet!

It's like when a person says, boat bat bot beat! You know, there's a change in the middle of each word that has to do with the shape and size of your palate when you say a vowel.

Uhh, how do they do that? Feel free to use words like aperture and gate and stuff, I know what they are.

Sounds like a normal synth thats being sent through a ring modulator. Use a squarewave and not a sinewave on the ring mod. And turn the frequency down so it's slow and not fast. Also the amount it's saturated with the mix is probably around 50% and not 100%.

I think that's what that is...I have a moogerfooger that I love to use with my guitar for fx like that. They also make a plug-in that simulates this. There are tons of ring mods out there. The one on the recording could have been on the synth itself.

Wow, thanks, House, you're a man of many talents. So, would the modulator be adjusted for each separate zot, or is it just the different angles of a square wave passing through slowly that makes it sound different?

To me it sounds like it could be rocking on the same square wave back and forth, but I only listened briefly. It sounds like what's giving the alteration in pitch is the synth thats being sent through it. I could be wrong here.

You can also automate the knobs/settings that adjust the rate and frequency to also modulate the way it sounds. This will definitely give pitch alteration.

..there's a very resonant filter 'modulating' the square wave (+ probably sawtooth) as well..some synths let you put two Lo Pass or Band Pass filters in series to get a more intense sound, can control filter by velocity, mod-wheel data etc.
Ring Modulators (good ears house!) (used on the Dr. Who Dalek voice) are groovy, and add a metallic overtone.

Ring modulators are sort of unstable sounding, so the articulation of each successive note can be radically different from the previous.