Korg NAUTILUS Series, Parameter Manual, Page: 313 / 961

Synthesis with the MOD-7: a guided tour VPM (aka FM)
303
VPM (aka FM)
Basic VPM
To start using VPM in earnest, simply connect the output of
one VPM Oscillator to the input of another. You can do this
either by selecting an algorithm, or creating a patch cable.
For instance:
1. Follow the instructions under “Creating an initialized
MOD-7 Program,” above.
2. Press the PAGE button and the MOD-7 tab, and then
press the Patch Panel button.
The Patch Panel will appear.
3. Set the Algorithm to 08: 2 + 2 + 2 -> Parallel Filters.
This groups the six VPM Oscillators into three carrier-
modulator pairs.
4. Press one of the VPM oscillator 3 jacks, and press the
ON check button at top right to turn it off.
5. Do the same for VPM oscillators 4–6.
This mutes VPM oscillators 3–6. From here, we’ll only be
working with VPM oscillators 1 and 2.
6. Press the PAGE button, the HOME button and then
the Tone Adjust tab. The PROGRAM > Home– Tone
Adjust page will display.
7. Press the Slider 9–17 button and lower Slider 9 to the
bottom of its range, and play the keyboard.
Lowering Slider 9 turns VPM Oscillator 1’s volume all the
way down. This means that you’ll hear only VPM Oscillator
2, which plays a pure sine wave.
8. While playing the keyboard, slowly raise Slider 9 to
the middle of its range, or slightly higher.
As you raise Slider 9, listen to how the timbre changes to be
increasingly bright. What you’re hearing is FM synthesis:
VPM Oscillator 1 is modulating VPM Oscillator 2. By
controlling the level of VPM Oscillator 1, Slider 1 controls
the amount of modulation.
In this algorithm, using standard FM terms, VPM Oscillator
1 is a modulator, and VPM Oscillator 2 is a carrier.
9. Press the Slider 1-8 button. While playing the
keyboard, very slowly raise or lower Slider 1.
Slider 1 controls the Ratio, or fundamental pitch, of VPM
Oscillator 1. Since VPM Oscillator 1 is acting as a
modulator, this changes the timbre of the sound.
10.Experiment with different settings of Slider 1 and
Slider 9.
Notice how Slider 1 changes the overtone frequencies
created by the FM, while Slider 9 changes their intensity.
11.Press the slider 1–8 button. While playing the
keyboard, press the switch 1 to turn it on and off.
This enables and disables VPM Oscillator 1. When it’s off,
you’ll hear VPM Oscillator 2 on its own: a pure sine wave.
When programming, this is a handy way to find out how an
individual VPM Oscillator is affecting the overall sound.
Feedback
Continuing from the above, let’s take a brief look at
Feedback . This causes the VPM Oscillator to modulate
itself, essentially acting as both the carrier and the modulator
at the same time.
1. Press the Tone Adjust Switch 1.
This mutes VPM Oscillator 1.
2. Play the keyboard.
Notice that the sound is now a sine wave, since we’re
hearing only the un-modulated VPM Oscillator 2.
3. Go to the VPM Osc 2 page.
If you’re still on the Patch Panel page, you can do this by
selecting any of the jacks on Osc 2 and then pressing the
Jump button in Parameter Details.
4. While playing the keyboard, slowly raise the
Feedback parameter to about 65.
Notice how the sound becomes brighter, almost like
sweeping the filter on an analog synth. In fact, when
Feedback is at 65, the sound is very close to a sawtooth
waveform.
You can modulate the Feedback level, and also choose
between two different feedback paths. For more information,
see “Feedback” on page 327.
Phase
In some cases, the phase relationship between the carrier and
modulator has an interesting effect on the sound. Continuing
from the above:
1. Lower VPM Osc 2’s Feedback to 0.
2. Go to the VPM Osc 1 page.
3. In VPM Osc 1, set the Ratio to 1.
Now, both VPM Osc 1 and 2 are set to the same Ratio, for
the most basic FM timbre: a carrier/modulator ratio of 1.
4. Press the Tone Adjust Switch 1.
5. Set the Tone Adjust Slider 9 to the middle of its range.
6. While playing the keyboard, slowly increase VPM Osc
1’s Phase from 0 to 90.
Notice how the timbre changes.
Phase has a strong effect with carrier/modulator ratios of 1:1
and 2:1, but is much more subtle (or not noticeable at all) at
other ratios.
Detuning
Let’s look at what happens when the carrier and modulator
are slightly out-of-tune. Continuing from the above:
1. Set VPM Osc 1’s Phase back to 0.
2. While playing the keyboard, use the + button to
change VPM Osc 1’s Freq Offset from +0000Hz to
+0001 Hz.
Notice how this introduces a chorus effect into the sound.
3. While playing the keyboard, use the − button to
change the Freq Offset back to +0000Hz.