Phase Modulation

Now it's time to fatten the sound. The oscillator section of the SubTractor is very versatileit allows you to adjust the phase modulation ("phase mod" for short) of each oscillator.

Huh? Well, each SubTractor oscillator can create a second tonea copy of itselfbehind the scenes. When the SubTractor combines this copy with the original tone, it creates a new, third tone. This is not the same thing as having four more oscillators. Rather, it's a process called phase offset modulation. What does it do? Despite its complex-sounding name, this process is simply a powerful tone-shaping tool.

The Phase knobs control the amount of the phase offset's effect, and the three-way switch next to each oscillator activates the offset and sets its type. The O position has no modulation (fat), the position has some (fatter), and the X position has the most (fattest).

For starters, let's listen to how the phase mode controls affect the sound of just one oscillator.

To set phase mod characteristics

1.	With your loop playing and Osc 1 enabled, click the Phase Mode button, or click to select the bottom mode O (no phase offset). When set to O, the phase knobs don't do anything because the oscillator isn't making any copies of itself.
2.	Select the middle phase mode () to hear a phase type called waveform subtraction. This adds high-frequency harmonics to the tone.
3.	Drag the Phase knob left and right to thin and fatten the sound (Figure 5.16). Figure 5.16. The oscillator Phase controls Technically, this nudges the oscillator's "tone copies" around in relation to the original. This is called adjusting the phase differential. When you use the middle () phase offset, turning the Phase knob to its leftmost position causes the oscillator tone to cancel itself out.
4.	For the most saturated, thickest-sounding phase offset, use the top (X) mode, or waveform multiplication.
5.	Drag the Phase knob left and right again. When you use the X phase offset type, turning the Phase knob to either extreme position causes the oscillator tone to cancel itself out.

Ring modulation

The SubTractor has a mode called ring modulation. Use it to get a brighter, more bell-like sound.

Ring modulation is like the X type of offset modulation, but instead of multiplying a signal by itself, ring modulation multiplies the Osc 1 and Osc 2 tones, creating difference and sum frequencies between the two oscillators.

There are no phase type controls for ring modulationit's either on or it's off.

To use ring modulation

1.	Make sure you have both oscillators enabled. The next step will increase the volume dramatically, so watch your ears!
2.	Click the Ring Mod button to enable ring modulation (Figure 5.17). Figure 5.17. Activate ring modulation to produce a bright, bell-like sound.