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A synthesiser is an electronic sound generating device capable of creating and manipulating electronic sounds. Most synthesisers are modelled on 1970s analogue hardware synthesisers. This means that they are made up of modules and control signals.

• An oscillator creates an initial sound according to a waveform (sine, triangle, sawtooth, square, pulse) which gives the timbre the oscillator also includes tuning controls (octave / coarse / fine)
• A synthesiser’s polyphony tells us how many notes it can play at once; if monophonic it will only play one at once
• Portamento or glide can be used to continuously bend between two notes on a synth
• A noise generator creates white noise; a random signal consisting of all frequencies at an equal amplitude
• It is used to simulate wind or percussive sounds like cymbals, and can also be filtered to create a sweeping effect (the cut off frequency is automated, resonance emphasises the sweeping); pink noise has accentuated LFs
• A filter shapes the frequency content of the signal coming out of the oscillator
• It is normal to see LPFs used to remove high frequencies but you often see BPFs and HPFs too
• The cutoff is the point beyond which it removes frequencies, measured when there has been 3dB reduction
• Filters are often labelled with two letters and a number, for example LP12; LP refers to the filter type and the number tells us about the filter’s slope (like the harshness), giving how many decibels it will remove per octave
• The resonance control adds a characteristic narrow boost of frequencies around the cutoff
• It accents a small frequency range and creates a ‘whistly’ sound that makes the signal close to the cut-off seem brighter and harsher; high resonance settings lead to self-oscillation where filter ‘creates’ a pitched note.
• Keyboard tracking is used so that the higher in pitch the note played on the keyboard, the more the filter opens
• An amplifier is used to control the volume of the signal; it most useful when routed to an envelope or LFO
• Control signals are not audible; they change a parameter on a synth module over time according to a shape
• Envelopes shape the sound by controlling a module parameter according to an attack, decay, sustain and release and thus how the note starts, sustains and finishes e.g. volume (amplifier), cut off (filter) or pitch (oscillator)
  • Attack – the amount of time taken to reach the maximum value for the parameter.
  • Decay – the amount of time taken to fall from the maximum value of the parameter to the sustain level.
  • Sustain – the level at which the parameter stays at whilst the key is being pressed.
  • Release – the amount of time take an to fall from the sustain level to 0 when the key is released.
• Synthesisers use an LFO to create a cyclic change in a parameter according to a shape, depth and rate; if controlling the oscillator, it can change the pitch, creating vibrato or pulse width modulation can give movement

Types of synthesis

• Subtractive synthesisers use an oscillator that can produce harmonically-rich waveforms which are then filtered
• Additive synthesis involves combining simple sounds (e.g. sine waves) to make a new one (e.g. Hammond organ)
• FM synthesis uses an oscillator called a modulator and an oscillator called a carrier and is good at creating sounds that are difficult to achieve with subtractive synthesisers – e.g. bell, pluck or metallic sound
• Sample-based synthesis is similar to subtractive synthesis, but uses a sample rather than an oscillator; wavetable synthesis can morph or evolve the starting sample over time. In granular synthesis, a longer sample is broken up into very small sections called grains; these are played in different orders / looped/ layered / omitted
• Revise chapter 8.4 to make sure you can identify the Theremin, Hammond Organ, Rhodes Piano and Clavinet

The impact of synthesisers

• Synthesisers were both used to emulate acoustic instruments and to create new and unique sounds; they defined the sound of electronic and dance music genres, such as techno, house, and disco
• Early monophonic / subtractive synths were most suited to basslines, leads and solos
• The Moog synthesiser was one of the first widely available electronic instruments
• The use of synthesisers also made production more accessible and affordable; one person could do everything
• Synthesisers were also used to experiment with new forms of music, such as electronic and ambient music
• Synthesisers shaped the big polished sound of pop in the 80s; they made it possible to create complex and layered arrangements. FM synths created of complex and rich timbres that were previously possible; synths became more affordable and accessible to professionals and amateurs alike
• In the 1990s, the Super Saw waveform setting in the JP-8000 formed the basis of trance
• VST (virtual studio technology) came about in 1996, leading to synth plugins; hardware synths started to go out of fashion because of the convenience and versatility of plugins
• However, there remains a demand for analogue synths; equipment worth little in the 80s now sells for £1000s.

Checklist

Using synthesis to create sounds

The sound and shape of waveforms (sine, triangle, pulse, square, saw)

Aurally identifying sine, square and saw waveforms

White noise

Shaping sound using a low frequency oscillator (LFO)

High pass and low pass filters

How an envelope can be used to control parameters of a sound

How timbre is affected by different parameters

The effect of cut off frequency and resonance and timbre

How amplitude and filter envelopes can change the timbre of a sound

Individual stages of an envelope (ADSR)

Mapping envelope and LFO to filter cut off frequency and pitch

Oscillator octaves, coarse and fine tuning

Pitch bend and pitch bend range

Monophonic and polyphonic synthesisers

Portamento

Arpeggiators

Comparing types of synthesis

Explain subtractive synthesis

Explain additive synthesis and how it relates to the Hammond organ

Define FM synthesis

Recognise FM sounds

A passing knowledge of granular, wavetable and sample-based synthesis

Keyboard instruments

Theremin, Rhodes piano, Clavinet, Hammond Organ

Development of music technology

The wider impact of synthesisers on the music industry