Example Patch: Granular Scrubbing
Since the STS can play fragments of a
sample as small as 8 ms, it can be used
for some basic granular synthesis
techniques such as granular scrubbing.
This can be used for a variety of sounds,
including time-stretching (without
changing pitch), and pitch-shifting
(without modifying playback time).
The simplest way to play with granular
scrubbing on the STS is to load a familiar
sample: a drum loop or a vocal sample,
perhaps. For starters, pick a sample
that’s between 1 and 10 seconds long.
1.Turn
Start Pos
and
Length
to 0%.
2.Hold
PLAY
to make the channel loop.
You should hear a buzzy tone.
3.Slowly turn the
Start Pos
knob up, and
listen how the sample is played
(scrubbed).
Start Pos
essentially is
sweeping the play head.
4.Now turn
Start Pos
down slowly. The
sample should play backwards! Notice
that no matter how fast you turn
Start Pos
, the pitch does not change. That is, you can play the
sample faster or slower without changing its pitch. This is time-stretching in its most basic form.
5. Now turn
Length
up a tiny bit. Hear how the buzzy overtone changes?
Length
is setting the size of
the grains.
6. Let’s use an LFO to sweep through the sample so you don’t have to do it by hand. Patch a very
slow ramp-up LFO into the
Start Pos CV
jack. A Pingable Envelope Generator is great for this. The
period of the LFO will equal the playback time, so make the LFO’s period several seconds long.
Make sure the
Start Pos
knob is back at 0. For full range, the ramp-up LFO should be 0V to +5V:
Set the PEG’s Scale knob to 3:00 and Bi-Polar off. Attenuate or shift as needed: any voltage under
0V or over +5V will make playback “hang”. When the LFO is exactly 0V to +5V, you should hear the
entire sample being played forwards. Adjust the LFO speed to adjust the playback speed. Also,
you can attenuate the LFO and/or adjust the
Start Pos
knob to select certain portions of the
sample to playback.
7. Try different LFO wave shapes: ramp-down will play the sample backwards, triangle will play it
forwards-backwards, curved waves will play it at variable speeds (constant pitch).
8. Next, let’s get rid of that buzzy overtone. Patch a random LFO (or a simple triangle if you don’t
have a random source) into an attenuator module. Attenuate the signal heavily, down to about
+0.5V max. Patch the attenuated random LFO/noise into the
Length CV
jack. Make sure the
Length
knob is turned all the way back down. The overtone should now be randomized enough that it
disappears. Adjust the attenuation and/or random speed and/or
Length
knob to suit your taste.
9. To change pitch without changing the playback time, simply adjust the
Pitch
knob (or use the
1V/
OCT
jack). Since the playback time is set by the LFO in
Start Pos CV
, you can freely adjust
Pitch
without changing the timing. Likewise, you can adjust the playback timing without adjust the
Pitch
.
Random Grains
Scrubbing involves playing the grains in order, but you also can play grains in random order. Patch the
random LFO into
Start Pos CV
instead of
Length CV
, and don’t attenuate it as much (or at all). Then
you can leave
Length CV
unpatched, or patch some other LFO into it to vary the grain sizes.
Page of
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To output
mixer
Random CV
(attenuated)
0V to 500mV
Hold to
Loop
LFO
(e.g. Ramp)
max 0V to +5V
