96 97Modulation Techniques
Sequential Prophet X User’s Guide
Modulation Techniques
6. With the LFO 3 parameters shown in the main display, press Soft
Button 3 to select the lfo dest menu tab, then select osc2 shape with
Soft Knob 1.
7. Set LFO 3 frequency to 72 and LFO 3 amount to 68. Note that these
settings differ from those set for LFO 2/oscillator 2
8. Play some chords. Basic PMW string sound!
To hear what a difference pulse-width modulation makes, remove it by
turning the LFO amount parameter for both LFO 2 and LFO 3 to zero.
You can use this technique to add harmonic movement to any of the
oscillator waveshapes, not just the pulse wave. But be aware that if you
set the amount of waveshape modulation too high on the pulse wave, it
will become so narrow that the wave’s sound will disappear!
Modulating the Stereo Filters Independently
Because the Prophet X has stereo lters (in 8-voice mode), you can add
even more movement by using the LFOs (or other sources) to indepen-
dently modulate the left-channel and right-channel lter cutoff. This
produces some interesting stereo ltering effects. We’ll re-use the same
two LFOs in the example below. The mod matrix makes it possible to
route the same source to multiple destinations.
To modulate the left and right channels of the stereo lters:
1. Start with the PWM string sound from the previous example.
2. In the modulation section, press the assign source button. Use soft
knob 1 to scroll to the rst available mod slot.
3. Use soft knob 2 to scroll through the various mod sources and choose
lfo 2.
4. Use soft knob 3 to set the amount to 20.
5. Use soft knob 4 to scroll through the various mod destinations and
choose cutoff l.
6. Now do the same for LFO 3 and the right lter channel: Use soft
knob 1 to scroll to the next available mod slot.
7. Use soft knob 2 to scroll through the various mod sources and choose
lfo 3.
8. Use soft knob 3 to set the amount to -20.
9. Use soft knob 4 to scroll through the various mod destinations and
choose cutoff r.
10. Hold a chord and notice how the sound moves as the cutoff frequency
changes on the left and right channels of the lter.
11. Increase the lter resonance to make the effect more dramatic.
Creating Sounds Using FM (Frequency Modulation)
Frequency modulation is a technique where the frequency of one oscil-
lator modulates another oscillator, producing complex harmonics. This
is how instruments such as the DX7 produced its sounds. In classic FM
instruments, sine waves were used. But because the mod matrix makes
it possible to route any of the Prophet X sound sources to each other
(including sampled instruments), the sonic possibilities are even greater.
To create sounds using frequency modulation:
1. Recall the Basic Program. (See previous examples if necessary.)
2. In the Mixer, turn up Oscillator 2 to 127.
3. Turn Oscillator 1 level down to 0. (Because we’re going to use it as a
mod source, we don’t actually want to hear it.)
4. In the oscillators section, set both oscillators to sine.
5. In the modulation section, press the assign source button. Use soft
knob 1 to scroll to the rst available mod slot.
6. Use soft knob 2 to scroll through the various mod sources and choose
osc 1.
7. Use soft knob 4 to scroll through the various mod destinations and
choose osc 2 freq.
8. Now, repeatedly play a note and listen to what happens while you use
soft knob 3 to slowly increase the modulation amount to 127. The
sound becomes more gong/bell-like.
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