Analog voice processing

[Jeremy Brookes]

>Does anyone know what effect was used for the voices of the Ceylons in
>Battlestar Galactica? It had a nasty metal-on-metal type sound. My initial
>guess is that this was done with a vocoder and synth. 
>
>I've heard versions of this effect at several different times, and I'm
>interested in emulating it.

>From what I can recall reading on this somewhere and from memory of what it sounded like, I believe it was done with Ring Modulation. I may be wrong of course...