In the previous column, we started tuning oscillators in various
This month let’s have some fun with bringing in transposed
oscillators using a performance controller. In today’s world of soft
synths, oscillator mixing is not as commonly thought of a “knob
assignment destination” as, say, filter cutoff or envelope release. On
analog synths like the Minimoog, though, those knobs were right there in
your face, encouraging realtime tweaking. Bringing tuned intervals in
and out freely, at choice spots in your solo, is a very nice way to add
variety to your synth leads.
Click thumbnails for larger images below.
Fig. 1. Rob Papen Predator offers level control per
oscillator. In the circled area, a modulation matrix slot is used to tie
oscillator 2’s output to a foot pedal.
Fig. 2. The center area of Novation V-Station is the oscillator level mixer, which we have a dialog open to modulate.
Fig. 3. Modulating the mixer knob for oscillator 3 using a foot pedal in the matrix (top area) of Gforce Minimonsta.
Fig. 4. On most Korg workstations, each oscillator has its own filter path, so the output levels are in the filter section.
Fig. 5. A matrix setup to bring the main layer down and
the tuned-interval layer up using a single controller, in Spectrasonics
Fig. 6. Dialogues open for this same technique in Applied Acoustics Ultra Analog.
Where are the Levels?
Right off the bat, I need to point out that not all synths
and soft synths can do this technique as part of their voice
architecture. You don’t just need knobs to control the levels of each
oscillator—you need the ability to modulate each of those knobs
independently. In researching this column I found a number of soft
synths that don’t provide this. Here’s a plea to synth designers to
build this in via a modulation matrix, or mixer design of some sort.
True, you could still MIDI map knobs on your controller directly to
oscillator levels, but since this normally isn’t saved per patch (unless
you want to get into programming and saving presets on your MIDI
controller), it ties up those knobs for all your sounds. So, where do we
find the level controls on soft synths that can modulate them?
In the oscillators themselves. Rob Papen’s
Predator, for example, is organized this way. With the abundant slots in
the modulation matrix, you can bring in a second oscillator or even
cross-fade oscillators all under the control of a single modulator. In
the circled area of Figure 1, a foot controller (CC 04) is
bringing up the level of oscillator 2 (Mod 2), which we’ve pre-tuned a
fourth down. Oscillators 1 and 3 are providing the same base pitch, but
they’re slightly detuned to produce a nice, fat sound. Don’t be confused
by the fact that oscillator 2 shows a given level set as a default—it’s
set that way to produce a smoother response from the pedal, so the
oscillator comes in faster, earlier, or more smoothly. With your pedal
heel to the floor (minimum) the oscillator level is -40dB, which can’t
be heard alongside the other two oscillators.
In a mixer section. Taking after the Minimoog, many
soft synths use a mixer instead of putting oscillator level knobs in
the oscillator sections themselves. Can the mixer levels be modulated?
If they don’t seem to be onscreen, remember that we can likely do this
via MIDI Learn. In Figure 2, I have set up the same type of sound
in Novation’s V-Station and then used the automation feature in my host
(Apple Logic Pro in this case) to control the mixer level of oscillator
3. If you play a hardware Minimoog or Little Phatty, you could just
reach for the mixer knob when you want to bring in the tuned oscillator.
The best software virtualizations add more advanced capabilities, so I
can do this easily in Gforce Minimonsta (Figure 3), or Arturia Mini V, thanks to their modulation matrices.
In the filter? Yes—there might be an output level
for the filter that can be modulated. This is how most of the oscillator
on/off and fading is programmed in Korg’s M3, M50, OASYS, Kronos, and
Krome keyboards (Figure 4). This only works if each oscillator
has its own filter path; if all your oscillators go into the same
filter, you’ll need to use one of the other techniques.
Filter fake-out. If you do have separate
filters, but the filter output isn’t available as a modulation
destination, the filter cutoff can fake oscillator level control. The
idea is that a completely closed lowpass filter will pass no signal, so
it’s like the sound is turned off. As you open the filter you start to
hear the sound, and the amount you modulate this will bring your sound
to the desired “level” you want, based on brightness. I wouldn’t use
much (if any) filter resonance when doing this, as you simply want to
hear the tuned oscillator come in, not have its frequencies swept with
Once you’ve found how your hardware or soft synth
modulates oscillator outputs, try it and practice incorporating it into
your playing. One technique I like is to play a phrase “plain” and then
play it again with the added tuned interval. It’s like a
call-and-response between two players. It also works well to change
octaves for one of the phrases; try playing the “plain” version down low
and then answer it an octave higher with the added interval.
Fade to Feedback
Taking the concept a step further, you can fade out your
primary oscillator(s) as you bring in the tuned interval. Among other
cool uses for this, it’s key to simulating the sound of guitar feedback.
For performance reasons, you want to do both fades using the same
physical control. So, whatever controller you’re using to fade in the
transposed oscillator, it needs to be assigned to control the level of
the primary oscillator(s) as well, but in reverse fashion.
If your soft synth has a modulation matrix, this should be
easy. You simply assign the same controller to the desired parameter
(oscillator level, mixer level, filter output, etc.) but with a negative
modulation value. Figure 5 shows a setup in Spectrasonics
Omnisphere, using CC 02 (breath controller) to fade out layer A by
inverting the modulation value, while fading in layer B.
With MIDI learn, this may be more difficult, as some
synths don’t allow the inverting of the modulation range, or the same
controller being assigned to two different destinations with an inverse
response to one of them. One synth that does allow this is Applied
Acoustics Ultra Analog, and Figure 6 shows the setup that makes this happen.
Oh, and let’s not forget to tune the second (or third)
oscillator to a higher pitch. Common choices are an octave higher (+12
steps) or an octave and a fifth (+19 steps). Add a touch of delayed LFO
vibrato and you’ll be on your way. Since feedback is a very pure sound
harmonically, you can use a simple sine wave for the tuned oscillator,
but that’s not a hard rule. Do what sounds good to you. Until next
month, happy soloing!