The SubTractor Analog Synthesizer is one mean sound-generating machine, based on subtractive synthesis: two oscillators generate a "raw" waveform (e.g. a sine wave or sawtooth wave), which is then passed through several audio filters which alter the final result. Apart from the 2 main oscillators, the SubTractor also contains a noise generator, high-pass filter, low-pass filter, band-pass filter and notch filter possibilities, 2 LFOs and several ADSR envelopes.

You can also load patches into the SubTractor that contain certain pre-set settings. There's a lot of these in the Reason Factory Soundbank, sorted by category (e.g. bass sounds).

The Oscillator Section

The Filter Section

A low-pass (lp on the subtractor) is a filter which passes low frequencies, but reduces (or rolls-off) frequencies higher than a specified "cutoff" frequency. The cutoff frequency can be adjusted with the slider, allowing you to choose the amount of high frequencies to cut away.

Besides cutting away the frequencies higher than the cut-off point, one can also determine to boost the frequencies near this cut-off frequency. The amount of this boost is dertermined by the resonance setting of the filter. If you raise this one too much, you'll find some frequencies boosted so hard it hurts your ears!

High-pass (hp) does the opposite, cutting low frequencies and allowing only the frequencies higher than the cut-off.

Band-pass (bp) passes all frequencies that are around the cutoff, reducing both the lower and higher frequencies.

Notch is the opposite of Band-pass, reducing only the frequencies around the cut-off.

ADSR or the envelopes

Amp Envelope

The Amp Envelope is responsible for shaping the volume/level of the sound based on where the main Level slider is.

• A=Attack: This is the amount of time it takes to reach maximum volume. When the slider is at 0 it takes no time at all, going from no volume to full volume instantly. As the slider moves up towards 127, it will take longer and longer to arrive at maximum volume.
• D=Decay: The Decay slider determines the amount of time it takes to reach the Sustain volume (which is determined by the S slider).
• S=Sustain: The Sustain slider determines the volume of notes where you hold the notes longer than the Decay time. The slider determines its value based on the main Level slider. This means for example, if the Level slider is at 64, and the Sustain slider is at 127, the final level will be 64 (100% of the Level slider) Unlike the other sliders, the Sustain slider isn't really based on time, but is dependent on the Decay time and the Level slider amount.
• R=Release: The Release slider will determine how long it takes for the volume to reach 0 from whatever the volume was when you release a note. At 0 the volume will drop from X to 0 instantly, while at 127 the volume will remain at X indefintely.

Filter Envelope

The Filter Envelope works in a similar way to the Amp Envelope, but with a couple other variables thrown in to make it interesting. Like the Amp Envelope (linked to the Level Slider), the Filter Envelope is linked to the Filter 1 Freq slider. However, while the Amp Envelope will always effect the volume, the Filter Envelope will only effect the Filter 1 frequency as much as is determined by the Amt knob with 0 being no influence at all and 127 being 100% influence. Furthermore, the Filter Envelope can be inverted by pushing the Filter Env Invert button. Normally the Filter Envelope will "open" (goes from X towards 127) the Filter 1 frequency; what the Invert button does is not invert the Envelope, instead it "closes" (goes from ''X" towards 0) the filter.

Also worth noting is that the Filter Envelope shape can be sent via CV signal to anything that accepts CV by flipping the rack around and using the Filter Env Modulation Ouput CV.

Mod Envelope

The Modulation Envelope behaves exactly the same as the Filter Envelope except that it is internally routable to any one of several possible destinations which can be selected by clicking the Dest button. Furthermore, it can actually be applied to more than one source when using the Mod Env Modulation Output CV on the back of the Subtractor.

LFOs

LFO stands for Low Frequency Oscillator and is basically a way of modulating something. It is possible to route both LFOs 1 and 2 to a variety of places internally and you can externally route LFO 1 to anything that accepts a CV signal via the LFO 1 Modulation Output on the back of the Subtractor.

LFO 1 is the "main" LFO on the Subtractor, there are several different shapes you can choose from, as well as different destinations. The controls are simple, Rate will adjust how fast the LFO shape cycles, from very slow to very fast. Amount will determine how much the LFO shape effects the modulation of the destination. The Sync button will not only lock the LFO rate to the tempo found in the Reason Transport, but also keep the LFO from triggering for each note played. When the Sync button is not active, LFO 1 is essentially polyphonic, that is it starts a new LFO cycle for each note played while continuing any LFO cycles already going.

LFO 2 is quite similar to LFO 1 in several ways in that you can manipulate the Rate and the Amount and the Destination. However, you cannot choose the shape of LFO 2, nor can it be synced. However, there are two other knobs available for LFO 2 that make it quite interesting. The Delay knob is used to determine the amount of time before LFO 2 begins to modulate its destination: at 0 there is no delay at 127 there is about 1.5 seconds before LFO 2 starts. The Kbd knob determines how much the pitch of the note being played effects the Rate of LFO 2. For example, if the Kbd knob is at 0 the Rate of LFO 2 will stay the same regardless of the note played, while at 127 LFO 2 Rate doubles per octave (i.e. C3 will have half the rate of C4).