Subtractive Synthesis

Do you want to be able to create your own subtractive synthesiser sounds and patches but not sure where to start? Do you want do be able to modify subtractive synthesiser presets to suit your tracks? We have developed the following guide to help you understand the different concepts of subtractive synthesis and how they all fit together to produce the final sound.

Subtractive synthesis is easily the most common form of synthesis around, with many different hardware synthesisers and plug-in synthesisers making use of subtractive synthesis techniques. Some examples of commonly available subtractive synthesis software and plug-ins include Ableton Live 8's Analogue, Native Instruments Massive and Pro-53, Novation V-Station, Reason's Subtractor and many, many others.

Although different hardware subtractive synthesisers and plug-ins all provide different user interfaces for interacting with and controlling the sound, the underlying concept of all subtractive synthesisers is the same. The final sound is created by starting with a harmonically rich waveform, such as a saw wave or square wave and using filtering and envelopes to shape the sound, much like a sculptor starting with a big block of stone and chipping away until the final sculpture takes shape.

A typical subtractive synthesiser has one or more oscillators to create the initial sound, and are typically fed with notation information (for example with MIDI or OSC). One or more filters to tonally shape the sound, as well as an amplifier to control the volume level of the output. Most subtractive synthesisers also provide a number of different envelopes, which can include pitch envelopes that control the pitch of the oscillators, filter envelopes that are either controlling the filter's cut-off frequency or the level of effect the filter has on the sound, and amplifier envelopes that control the volume of the sound over time. The layout of a typical simple subtractive synthesiser is shown below:

• Oscillator: As mentioned, a subtractive synthesiser typically has one or more oscillators. The oscillators typically produce waveforms such as sine waves, square waves, triangle waves and saw waves, although some subtractive synths also offer the use of wavetables or other waveforms. Most oscillators allow you to adjust the pitch of the sound (relative to the received notes), as well as allowing detuning of the oscillator. Pitch or frequency modulation is also a commonly found feature of oscillators, helping to add movement to the sound, along with the pitch envelope which can allow you to produce such effects as the pitch starting off high and dropping down as the note plays.

• Filter: A typical subtractive synthesiser filter allows you to shape the output of the oscillator using a variety of different filter types, including highpass, lowpass, bandpass and notch filters (for more info on filters, see our article on filters in our FX explained article). The filter can be typically controlled using the filter cut-off envelope, allowing effects such the filter cut-off sweeping through the frequency range as the note plays.

• Amplifier: The amplifier and amplifier envelope are used to dynamically shape the sound, whether you are after a sound with a sharp attack, or one that fades in, or maybe you are after a sound the takes a while for the sound to die off after the end of the note.

Most typical subtractive synthesisers also offer some form of modulation to allow you to add further character and movement to the sound. Generally this is offered in the form of low frequency oscillators (LFOs), or oscillators with a selectable waveform that cycle at a much lower speed than the main oscillators. The LFOs can typically be used to control other elements of the synth, for example pitch modulation and filter cut-off or filter resonance modulation. Some more advanced synthesisers also offer step sequencers and other devices that can also be used to modulate other synthesiser parameters.

Feel free to mess around with the different controls on your favourite subtractive synth and see what you can come up with.