MOTM

> "...A special switch [on the Moog 914 Fixed Filter Bank, the filters for
the
> Synthesis half of the vocoder] can alter the phase of the stages, which is
> the best situation for vocoding, but not neccessarily for the usual uses
of
> the 914..."
>
> Does anyone know what this means?

Hmm, I thought I should know, but I really don't.
Phase relation from one band to the next is highly important in a vocoder
(and it's often overlooked by beginners who want to build their own
vocoder) - BUT the same thing is true for a filterbank.

> On a related note, what exactly was the Roland Vocal Filter? Anybody? I
> believe JH built a clone of one, but I haven't been able to find anything
> about the thing at all.

It's the filterbank for vocal formants from the Roland Vocoder Plus VP-330.
This is *not* part of the VP-330's vocoder section, but an extra filter bank
for human voice simulation. (Big surprise for me - I thought they just
had some kind of preset for the vocoder.)
There are 4 selections of human voice, male and female in different ranges,
and these are fed from different octaves and different waveforms (!)
in the VP-330. I build my clone with 4 separate inputs, each normalized
to the previous, so I can use separate input signals, or just use the first
input for all 4 options, and have a bypass switch to run the signal
unchanged.
There's also a VCA and single-trigger mode AR envelope, so you can even
get a slow attack "ahh" choir from gated (organ-like) input signals.
Of the 4 sounds, 3 are so-so, but the 8' Male is awesome - it turns any
string-like synthesizer sound into a convincing "Vangelis" choir.

I don't plan to publish the circuit - you still can get the original schemos
from Roland.

Maybe I'm selling the box at some time (I have two vocoders which can
basically do the same thing), but if I do it will not be cheap, as I spent
hundreds for an engraved custom front panel, toroidal transformer and
so on.

JH.