stereoizing mono loop with vortex

[buzzard@world.std.com (Sean T Barrett)]

A sidenote:
 As a new owner of both a JamMan and a Vortex, I want to
 give many thanks to everyone involved with this list (and the website)
 for being such fabulous sources of information (and used gear).
 I've never bought equipment I'd never tried out with such a good
 understanding of what I was getting.

[This is kinda long, and totally Vortex specific...
it's not the looper you're looking for... move along.]

I had been expecting that I was going to use the Vortex
as a "performance expression effect" on my guitar sound;
however, until I get an expression pedal for it, this
probably won't happen, because I've gotten hooked on
placing it _after_ my JamMan, and using it to give the
(long) JamMan mono loops a stereo field.  This will probably
be less interesting if I were to play live with the
setup, but it is especially appealing when I'm playing
late at night with headphones (and it's _plausible_ I'd
be willing to consume half of my 4-tracks tracks on a
single loop).

My goal is/was most definitely to achieve the "sound" of
a stereo loop, so I don't care (for this purpose) about
changing the effect dynamically.

Initially, I used the Vortex as a glorified stereo chorus.
Then I hit on the notion of using the Vortex's delays as
a "sustain" in the sense of performing volume-swelled notes
so that they blend seamlessly with the delay.  The reason
it's interesting to do this in the Vortex (as opposed to
actually embeddeding it into the loop "proper" as it's
stored in the JamMan) is that it means that the note coming
into the Vortex is shorter.  Thus, if there is some kind
of dynamically changing effect "at the front" of the
Vortex, the shorter note will be "mostly the same", and
then the echoes will hold it out; if the echoes were
"stored in the loop", then the note would pick up the
changing sound.

To put it in a different, maybe more clear way: if I play
two overlapping notes (as heard through the Vortex),
each of which lasts for 5 seconds, and the second starts
two seconds after the first--if you "sustain" the notes
outside the Vortex, then during the 3 seconds the notes
overlap, they'll be processed identically--making it
sound like a mono loop with stereo processing.  If each
note is actually 1 second long, with the Vortex "echo
sustaining" it for another 4 seconds, then those two
notes can sound "independent" if there's an effect that
has changed sound in the intervening 1 second.

To be more specific, the idea I had in my head (which I
am about to describe trying to implement) was that a Vortex
patch with an LFO-panner on the inputs, and the delays
arranged as a true stereo echo, would make it so that each
note played into the Vortex would come out at a random
location in the stereo field; tuning the panning speed
makes sure that the notes don't move too much during the
time they're actually at the input of the Vortex (and
going through the panner).

I.e., conceptually, I want the whole system to sound
like I have a "stereo JamMan", and each note added to
it is placed at a different position in the stereo field.
The actual description above achieves that, except that
when a loop repeats, the stereo position will change
(since the timing of the loop and the panning LFO aren't
in sync).

So, I hunt through the list of effects for something
that does this.  The best I find is (I assume now, I
didn't take notes) Maze A, which is basically this,
except that (according to the chart) the echoes are
connected L&R reversed from the direct signal.  That
could be coped with by not mixing in the direct signal.
However, it seemed that the echoes simply did not have
the same stereo separation that the direct signal did,
and I couldn't quite figure out why.  This could have
been user error, but I found a substitute--Cycloid A,
which does "filter panning", worked pretty well.  The
effect was interesting, and did give an interesting
stereo quality to the loop--a very different kind of
stereo than just "glorified stereo chorus".

Well, I thought that was the end of that, so I ignored
my JamMan and decided independently, for fun, to try
to make a Vortex patch with the Vortex looping but
some internal effect on the feedback, so that the
loop would get progressively "nastier" (for a
definition of nasty meaning multiple passes of some
effect).  The choices for algorithms that do this
are extremely limited; unless I'm forgetting one, just
Shadow A, which has an _unconfigurable_ hicut filter
in the feedback loop, to simulate tape echo, and
Atmosphere B, which has two modulators in the feedback
loop, and 7 parameters affecting them!  Sounds great.

So then I wasted a bunch of time trying to figure
out the parameters did.  (Where "waste" is defined
as "I never did understand".  Anyone care to attempt
to explain _what_ a modulator is, and then hence
what a _tap_ is?  I'm assuming the difference
between a tuned tap and a gliding tap is simply
that the former is fixed and the latter has a
parameter that is swept with the LFO.)  I pretty
much failed to get any kind of interesting "each
time it repeats it gets nastier".

To connect back to how this started, however, I did
accidentally create a surprising looping effect which
I didn't even think was possible with just a pair of
delays: a stereo echo where each echo occurs
at a different location in the stereo field.  That
is, the first echo is basically in the center, the
second is a little more to the right, etc., until
they're mostly on the right; then they move back
across to the _left_.  If it weren't for that last
bit, you can get a similar effect simply with two
delays configured in stereo, with different feedback
settings (one channel dies away faster, and the sound
"moves" to the other side); however, that effect is
much less dramatic.  It's also not like the sound
of Mosaic A, where the echoes are glued to the
location of a panner controlled by an LFO; each
note sounded makes this progression independently.
[It may be that this effect is trivially creatable
with the Vortex, and I just happened to find it as
part of Atmosphere B; however, I was not able to
construct it in any other algorithms, although I
didn't try very hard.]

The upshot of this is that with the "use a delay
to simulate sustain", you get a note which starts
at the center of the stereo field, then slowly
moves one way and then the other.  Put the mono
looper back in front of that, and you get an effect
indistinguishable from what you would feeding that
same patch into a true stereo looper, and you get
a very interesting (and continuously shifting)
stereo field, as opposed to the "subtle fixed" chorusy
sounds or the "dramatically shifting" panning sounds.

Anybody got any other tips or tidbits for putting
Vortex post-JamMan, or in general applying stereo
effects to mono loops?

Sean Barrett
(of course two echoplexen is the right way to stereo loop, but
I can't really justify such a purchase solely to get stereo
looping; although I suspect there's at least one in my future)