#5. Synthesizers in Reason - Subtractor

In the next 3 tutorials we are going to familiarize ourselves with the synthesizers in Reason. I strongly recommend that you take a look at the “Basic Synth Concepts” tutorial first which covers most of the similarities between them, since we are not going to discuss those in the following tutorials.

The Subtractor is the first synth made in Reason. It is a mono device which uses subtractive synthesis for the creation of its sounds. In simple terms, subtractive synthesis is creation of sounds in which different waveforms are processed trough filters. Additive synthesis on the other hand uses a combination of different harmonic basic sine wave tones in order to create the other types like sawtooth, square, etc. For example, if you want to create a sawtooth wave, you need to add many sinewaves – each new added with doubled frequency and amplitude (volume) being 1 / 2, then 1/ 3, then 1/ 4, etc…

Adding different harmonic sine waves together (using the Fruity Loops oscilloscope to show you what changes take place). The ending waveform looks more and more like a sawtooth waveform. The more waveforms are added, the better quality sawtooth we have in the end. The sinewave is the most basic tone (it is actually one dimensional circle).

After that healthy sound creation tip we are going to go back to the Subtractor device.

The Subtractor synthesizer has 2 oscillators with 32 waveforms (including the 4 main sawtooth, square, triangle and sine) and a noise generator. You can select octave transposition, semi-tone (the interval between two adjacent keys, for example C4 and C#4) and cent which divides the semi-tone into 100 fractions.

There was a very neat article in the web from which I`ve print screened all the subtractor waveforms visuals (I can`t find it on a web anymore, so I can`t give the link :( ).

Subtractor`s special weapon is called Phase Offset modulation. When you turn it on, you create a copy of the sound waveform and move it off sync relative to the original one either positively or negatively (using the phase knob). The 0 sign means the effect is off, the "–" sign means that the effect uses subtraction and the "x" knob means that the effect uses multiplication.

Oscillator Mix determines the levels of the two oscillators relative to each other (note that the noise generator and the ring modulator amounts are on the side of the second oscillator in the mix, so if you turn it all the way to the left you won`t hear them).

The noise oscillator is used to create… noises. It has a decay knob determining its duration while the key is pressed, color (from low to bright) and level knobs. On an initialized patch – if you turn the mix knob all the way to the right and turn on the noise generator you will hear it exclusively (alternatively, you can use a little bit of hack – initialize the patch, set oscillator 1 to square wave, make a negative phase offset and turn the phase knob all the way to the left – that will also mute it).

You can use the Kbd tracking button to disable the input of notes from your midi keyboard, making it play a constant pitched sound regardless of the note (for example you may use it if you create a synth percussion sounds requiring constant pitch) .

(Note that the noise generator doesn`t change it`s pitch regardless of whether Kbd tracking is turned on or off).

FM stands for frequency modulation. In it one waveform (modulator (oscillator 2 in Subtractor)) controls another one`s frequency (carrier (oscillator 1 in Subtractor)). It`s a little bit like an LFO although you can hear the sound of the wave that does the modulation. If you don`t want to hear it, simply move the mix knob all the way to the left to hear only oscillator 1 (rather than turning off the oscilliator 2 which will stop the modulation). Since oscillator 1 is the carrier you will not hear the effect if the mix knob is turned all the way to the right which will mute oscillator 1 relative to oscillator 2.

To test that, turn on the FM knob a bit (lets say - half way) and start the second oscillator. Move the mix knob all the way to the left in order to hear only oscillator 1. Now when you play a note and make changes in oscillator 2 you will hear difference in the frequency modulation despite the fact that oscillator 2 is muted. If you do the opposite – mute oscillator 1 relative to oscillator 2 with the mix knob and make changes in oscillator 1, you will not hear any changes in the sound.

Ring Modulation is a type of amplitude modulation in which two waveforms are multiplied (one is usually sine or some other main waveform). The resulting signal contains the sums and the differences of the oscillators` frequencies (ex. - if oscillator 1 has frequency of 11 kHz, and oscillator 2 of 200 Hz, this will output result containing 1,3 kHz and 900 Hz).

In the case of Subtractor, the ring mod is applied only to the second oscillator, therefore you will hear it`s effect only if you can hear oscillator 2 in the mix (unlike the FM case where the opposite happens and the oscillator 1 is the main player). To prove that you can make similar test as we did with the FM synthesis – turn on ring mod and mute one of the oscillators and make some changes to the other one and see if there are differences in the sound output.

The name Ring Modulation comes from the appearance of the diode scheme used to achieve that effect in electronics – they are placed in a form of ring – very similar to the Graetz bridge rectifier trick used to transform AC to DC.

Subtractor has the standard envelopes and filters we have discussed before. The LP12 and LP24 of the low pass filter determines the resolution of the filter in decibels (all the others are at 12 dB). If you link the 24 dB LP filter to the Filter 2 and turn it`s frequency all the way down you will have 36 dB filter. The filter has it`s own kbd knob which modulates it by the note being played. It has amp envelope (for the level), filter envelope and mod envelope affecting selectable target. The last two have amount knob and an inversion option.

Subtractor has two LFOs – the first one has six waveforms which can affect six targets and two knobs – one for the amount and one for the rate. LFO2 has the ability to increase or decrease its rate, depending on the note being played (enabled by the Kbd key track knob). By default it has only a sine LFO wave. It also has a Delay knob which is something like an Attack of the effect determining how long it will take for it to take place when the key is being pressed.

Lo BW (Low Bandwidth) cuts some of the higher, less noticeable sounds in order to save some CPU power. It is located near the patch selector. 

Subtractor can control different targets with received After Touch, Expression Pedal and Breath Control MIDI sources.

If you press TAB and look at the back of the device you will see that it has a single mono output. You can stereo-lize it either by routing it in the left mixer channel or by using audio merger. It has modulation cv and gate inputs and modulation outputs.

P.S. Subtractor has a special "unscrew screws" function which you can do with the left mouse button.