Could be a flanger or phaser. I would use a Leslie but that's just me.

whats a "Leslie "

A speaker mounted in a cabinet with a rotating baffle underneath. Big, expensive and bulky but there are plenty of digital effects around that simulate a Leslie cab.

So what kind of digital effects are you talkin' about .. hahah sorry for asking so much

What platform are we talking about? Mac? PC? VST? AU or RTAS? If VST, there is a plugin suite by [[url=http://[/URL]="http://mda.smartele…"]MDA[/]="http://mda.smartele…"]MDA[/] which includes a Leslie emulator. Doesn't sound bad but not quite a Leslie. There are other rotary speaker emulators. A phaser can be set up to sound like one. The best Leslie emulator I've yet heard is the DB33 Plugin that comes with ProTools LE. 8.

Once upon a time the only option was to try a bunch of effects until you found something you liked. In those days you had to reverse engineer other peoples' effects. You learn a lot more that way compared to just getting online and asking those of us who did it the old way to give you easy answers. Better yet, you might put together a unique combination of effect so original it gets named after you, securing you a place in the sound engineer pantheon.

But, yeah, Leslie, rotary speaker, phaser, flanger or some other modulated effect.

Sounds like there is a short delay there as well. Tuning plugins can also give you these kinds of artefacts if used moderately and correctly. Try stacking a phaser, a leslie emu, some delay, tweak the tuning till you hear some artefacts and run it though a compressor as well like a 1176 with the "4" button pressed, shortest attack and longest release so that the meter hovers around 12 or so.

Might work, havent tried it out myself so I might be pissing into the wind, but you live and you learn.

PS: "Tuning plugins can also give you these kinds of artefacts if used moderately and correctly." correctly uncorrectly... if you get my drift...