As we covered in the April 2013 column, you need to fade
out the main oscillator(s) when you want to simulate feedback, and
Jordan does this using an effect rather than modulating the amp output.
Why? I’ll explain a little later. Using two Stereo Limiters he has one
set to cut the volume when pushing the joystick up (JS+Y) and another to
cut the level when pulling the joystick towards you (JS-Y). This is
done by modulating the gain stage within the limiter negatively when the
controller is moved. Either way you push the joystick, the main sound
fades out, leaving room for the feedback tones.
The basic tone of the feedback is produced by an AL-1
program with a pulse wave set to 50 percent width, tuned up an octave
and a fifth. This is a nice, hollow sound—perfect for simulating
feedback, and a bit stronger than using a sine wave. That oscillator
produces no sound when a key is depressed; only the movement of the JS+Y
raises its amp output. A second oscillator is set to the same waveform
but is only tuned up an octave, so it sounds below the main pitch and
only comes in via pressure, so you can sweep into the feedback using the
joystick, and then slowly add the additional harmonic using aftertouch
as you wish. Nice!
Even hipper, Jordan Rudess uses the ribbon to introduce
some ring modulation to the sound, with a setting called AM—which is the
traditional ring modulation between the two oscillators plus the
original carrier wave’s dry signal mixed back in. Listen to it being
demonstrated online; it’s a cool extra bit of “drama” added to the
sound. Remember that the ribbon added a sub-oscillator to the regular
sound, which goes away when the harmonics are introduced, so he reuses
the ribbon for this coloration.
The feedback shares the same spiked amp envelope for that
punchy attack, and nothing special is happening for the filter, since he
wants the sound to remain pure and open the whole time. A second
instance of the AL-1 (the Kronos can stack two sound engines, either
different or the same, in a single Program) uses similar settings, and
is brought in via the JS-Y movement. Here the main oscillator is tuned
up two octaves, with the pressure-induced second oscillator tuned up
only one octave. The ribbon again introduces the ultra-cool AM ring
Fig. 1. The effects chain for the main lead sound.
|Fig. 2. The effects chain for the feedback sound.
|| Fig. 3. Using the Kronos’ secondary (vector) joystick to bring in an extra sync sound.
Whole Lotta Oscillatin’ Goin’ On!
The benefit of using separate programs is becoming
apparent, as Jordan is using a lot of oscillators to produce the cool
variations in the sound, and no single program would offer that many
resources. But playing this sound on an 88-note keyboard introduces
another issue that’s solved by using multiple programs. As Jordan moves
far up and down the keyboard, the feedback tone moves out of its “sweet
spot,” so he uses multiple copies of the sound and shifts their pitch so
they repeat halfway across the range. The upper end of the keyboard is
tuned an octave down, and covers notes G#4 to G9. The middle of the keyboard is set to “zero” tuning, and covers G4 down to E3, effectively repeating the same pitches. A third copy of the program is set to play from D#3
down to the bottom with the same tuning, but with a much lower volume
in the mix, taming its output when he wants to go way low.
Let’s tally up the total oscillators involved here: The
main sound uses two detuned oscillators, with a third one acting as a
sub-oscillator, or simply tuned down an octave. The feedback Program
uses two oscillators for the JS+Y/aftertouch sound, and another two for
the JS-Y/aftertouch sound, so we’re up to seven oscillators. The
repeated copies of the feedback each use two oscillators (two times
three instances equals six), so in total we have 13 oscillators in
Another benefit of creating this sound in a Combi (a
multi-sound stack that might be known as a Performance, Multi, or Setup
on synths other than the Korg Kronos) is for flexible effects routing.
Very few synths offer the ability to route each oscillator to its own
effects chain. Since Jordan is using the Kronos’ Stereo Limiter effects
to fade out the main sound, he needs to be able to route different parts
into different effects. So, the feedback tone doesn’t go through those
limiters. He runs the feedback tone into a Tube PreAmp Model (within the
Kronos) for some extra warmth before it “joins” the rest of the
amp/distortion chain (see Figure 1).
Wait, There’s More!
To bring even more performance variation into the sound,
Jordan uses a knob to turn off both the Limiter’s gain reduction when
using the joystick’s Y-axis (the knob sets each limiter’s mix to dry,
bypassing it), and brings in a second distortion effect—this time an
Overdrive with a built-in wah (see Figure 2). The effect isn’t
adding a lot more overdrive; he uses it for the wah component, sweeping
the wah open as he pulls the joystick towards him. So at certain points
in his solo he can abandon the feedback tones and revel in the wah and
the nearby sub0oscillator (via the ribbon).
This explains why he used Limiters to fade out the main
tone; if he’d done it via amp modulation at the oscillator level (as I
taught you earlier) he couldn’t easily switch that off when he wanted to
reuse the joystick to become the wah controller. Could he have left the
joystick to fade out oscillators and used a pedal for the wah sweeping?
Sure, but as he stands as he plays and likes to swivel his keyboard
around for dramatic effect. So, also trying to operate a pedal might
have made for some awkward stage poses.
As I explored the sound I found one other cool programming
trick that was in the main lead program, which Jordan had disabled in
the Combi. When I asked him about it, he confirmed that since it used
the rather small, secondary vector joystick on the Kronos he abandoned
it for live gigs, as he found it too hard to use the small stick
effectively in the heat of performance. However, this speaks to the
principles this column has been all about—introducing more timbral
variation during your solos—so Jordan agreed that we should share it.
In the main lead sound Program he used the vector joystick
to fade out the main AL-1 program, using amp level modulation. At the
same time he faded in a second instance of the AL-1, set to a similar
sound, but also using oscillator sync to add more edge (the slaved
oscillator was tuned down an octave, and the master oscillator is tuned
up three octaves and a fourth). This main sync sound is produced when
moving the vector joystick up and away from you (VJS+Y). Moving it down
and towards you (VJS-Y) brings up the same sync program but also retunes
the second oscillator to another pitch and introduces a slight amount
of FM. This gives you plenty of diverse timbral variation via the
controller. Listen to the audio examples below to hear the cool tones