"Shepard tone" in a phase/modulation pedal LFO?

[sfr]

I've was reading about Shepard tones and playing around with them in a sequencer/software synth.  Fun, interesting and basically useless stuff.   

It's beyond my ability to implement, although I'm trying to figure out how to ape it in software; but I started to wonder - could you do something similar with a phaser or some sort of modulation pedal - have the two notches moving "parallel"; equidistant as it were, and as one passed a certain point have it jump back that same distance on the other side of the first one?  (If this doesn't really make sense, the wikipedia link about shepard tones above should give an idea) I imagine with sawtooth LFOs set at the same rate in the same range at different start points in the sweep, this could happen.  I don't know - I'm curious if you could adapt the Shepard tone idea to get a modulation pedal of some sort that sounds somewhat like it's always sweeping in the same direction infinetly.  (basically, I'm hoping to inspire someone else into doing the hard work for me.  )

[gez]

I've swept filters in quadrature which gives a similar effect.  Sawtooth would be the way to go, though I used triangles to sweep 4 parallel filters (you get a pseudo-echo effect if they all cover the same range).

[Mark Hammer]

Read this: http://hammer.ampage.org/files/quad-shep.pdf

The current Boss PH-3 phaser implements a "barber-pole" effect quite nicely, except that it does so digitally.