Propellerhead Reason - 4.0 Manual de operaciones descargar pdf (Pagina 191)

SUBTRACTOR SYNTHESIZER

189

Phase Offset Modulation

A unique feature of the Subtractor oscillators is the ability to create an extra waveform

within one oscillator, to offset the phase of that extra waveform, and to modulate this

phase offset. By subtracting or multiplying a waveform with a phase offset copy of it-

self, very complex waveforms can be created. Sounds complicated? Well, the theory

behind it might be, but from a user perspective it is just a method of generating new

waveforms from existing waveforms.

A seasoned synth programmer using Subtractor for the first time may wonder why the

Subtractor oscillators (seemingly) cannot provide the commonly used pulse waveform

and the associated pulse width modulation (PWM). Or oscillator sync, another com-

mon feature in analog synthesizers. The simple answer is that Subtractor can easily

create pulse waveforms (with PWM) and oscillator sync-sounds, and a lot more be-

sides, partly by the use of phase offset modulation.

Each oscillator has it's own Phase knob and a selector button. The Phase knob is

used to set the amount of phase offset, and the selector switches between three

modes:

• Waveform multiplication (x)

• Waveform subtraction (–)

• No phase offset modulation (o).

When phase offset modulation is activated, the oscillator creates a second waveform

of the same shape and offsets it by the amount set with the Phase knob. Depending

on the selected mode, Subtractor then either subtracts or multiplies the two wave-

forms with each other. The resulting waveforms can be seen in the illustration below.

• In example 1, we see two sawtooth waves with a slight offset.

• Example 2 shows that subtracting one slightly offset sawtooth wave from the

other, produces a pulse wave. If you modulate the Phase offset parameter (with for

example an LFO), the result will be pulse width modulation (PWM).

• Example 3 shows the resulting waveform when multiplying the offset waves with

each other. As you can see (and hear if you try it), multiplying waveforms can pro-

duce very dramatic and sometimes unexpected results.

Using phase offset modulation can create very rich and varied timbres, especially

when used along with LFO or Envelopes to modulate the phase offset.

✪ To get a “feel” for this concept, you could study Patches that use phase

offset modulation, and maybe tweak some of the Phase Offset parame-

ters to find out what happens. Try “SyncedUp” in the Polysynth category

in the Factory Soundbank for an example of osc sync or “Sweeping

Strings” (in the Pads category) for an example of PWM.

! Note that if you activate waveform subtraction with a Phase offset set to

“0” for an oscillator, the second waveform will cancel out the original

waveform completely, and the oscillator output will be silent. If you set

the Phase Offset knob to any other value than zero, the sound returns.

1. The two offset

waveforms:

1. The two offset

waveforms:

2. The result of

subtraction:

3. The result of

multiplication:

Ampl.

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Propellerhead Reason - 4.0 Manual de operaciones Pagina 191

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