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Re: loop subtraction

At 11:48 AM -0800 3/10/99, Chris Chovit wrote:

>Perhaps there would be a way to just make the "subtrating signal" out of
>phase with the main signal, and this might create a similar effect, as the
>signals would cancel each other.  I can imagine the usefulness of
>this....loops can get pretty busy, and you could "thin it out" using this

Phase tricks are pretty easy, and probably do a lot of what you are looking
for. The neat thing is, it's actually rather hard to to get the whole
signal to match perfectly. The lower frequencies will cancel out pretty
easily, and then you'll have a bunch of higher frequency stuff left over,
which can sound pretty neat. Here's some ideas for this:

There are fun things you can do with two loopers.  You need one looping
source (which can be anything) and a second looper to record it into
(should be an audio looper), and some way to accurately sync the loop
lengths together. Then you need some way to invert one of them and mix them
back together. So you create your loop in the first one, then record it in
the second one, so that both have the same thing in it. Then mix them
together and play around. For your idea, maybe you'd want to send the
initial basic loop to the second unit (which might be left muted), then go
back to the first and build your loop up further. Then bring your basic
loop back, inverted, and mix it in to cancel out with the more complex loop
now in the first unit.

For me, the thing that is really interesting is that the methods you would
likely use to sync the two loops are probably not sample accurate. Midi
clock, for instance. Fine for rhythm, but not for phase. So what happens
is, the phase cancellations randomly change with each repetition of the
loop! To get this effect, you don't even need to invert the signal. For
example, sometimes I'll take my old drum machine, and play a drum loop with
the midi clock output and the audio connected to an echoplex. I'll record
the drum output in an echoplex loop, sync'd to the drum machine's clock.
Then just listen to the out put with the two playing at the same time.
Sometimes it's nearly perfectly in phase, and loud, sometimes its nearly
perfectly out of phase and very thin. Most of the time it's somewhere in
between. Very fun....   You can even record this effect in the loop, by
using overdub to add the same loop that you recorded in the first record.

>Maybe it could be done within an echoplex:  have an insert mode =
>"subtract", in addition to the reverse and other insert modes.

interesting, but it probably wouldn't do much. You really need to have the
second signal be very similar to the original, with the phase in some
consistent relation for this sort of thing to work. (or at least work in
some simple way where we don't have to write a buch of code to be tracking
phase of the two signals and trying to shift and align them and such.
ick..;-)  Use the trick above. Besides, insert mode is looking realy
crowded lately.

>  Kim, any
>new versions of the software in the planning stages?

Now, you know damn well I won't tell you. You think I'm gonna let something


Kim Flint                   | Looper's Delight
kflint@annihilist.com       | http://www.annihilist.com/loop/loop.html
http://www.annihilist.com/  | Loopers-Delight-request@annihilist.com