The synth glossary
Every knob, wave and bit of jargon in one place — in plain English, and cross-linked to where you can hear it.
Synthesizers come with their own dialect — cutoff, resonance, ADSR, FM. Here is the whole vocabulary in plain English, colour-coded by kind and cross-linked to the Academy topic and the instrument where each idea shows up. 73 terms in all.
A
Additive synthesis
synthesisBuilding a sound up from nothing by stacking pure sine waves at different frequencies and levels.
ADSR
shapingThe four-stage shape of a classic envelope: Attack, Decay, Sustain and Release. It shapes how a note swells in, settles and fades.
Amplitude
soundThe height of a wave — how loud it is. Bigger swings mean a louder sound.
Arpeggiator
rhythmA device that takes a chord and plays its notes one at a time, in a repeating pattern.
seeCascade
Attack
shapingHow long a note takes to reach full volume after a key is pressed. Fast is a pluck; slow is a swell.
B
Bandpass filter
shapingA filter that passes a band of frequencies in the middle and cuts everything above and below it.
BPM
rhythmBeats per minute — the tempo, or speed, of the music.
C
Carrier
synthesisIn FM synthesis, the oscillator you actually hear — the one whose pitch the modulator bends.
seeFM
Chorus
effectAn effect that thickens a sound by mixing in slightly detuned, delayed copies of it.
Cutoff
shapingThe frequency where a filter starts working — for a lowpass, everything above it is turned down.
seeSubtractive
D
DAW
gearDigital Audio Workstation — software for recording, arranging and mixing music. PlasticSynth's Studio is a tiny one.
Decay
shapingIn an envelope, the drop from the attack peak down to the sustain level.
Delay
effectAn echo effect that repeats the sound after a set time. Feed it back on itself and the echoes repeat.
Detune
soundShifting an oscillator slightly off pitch. Layering detuned copies gives a thick, shimmering sound.
E
Envelope
shapingAn automatic control that changes a value — usually volume — over the life of a note. See ADSR.
Euclidean rhythm
rhythmA pattern that spreads a number of beats as evenly as possible across a number of steps — the basis of many world rhythms.
F
Filter
shapingA tool that removes or emphasises part of a sound's frequency range — the heart of subtractive synthesis.
seeSubtractive
FM synthesis
synthesisFrequency modulation — using one wave to wobble another's pitch thousands of times a second, creating new harmonics.
Frequency
soundHow fast a wave vibrates, measured in hertz. Frequency is what sets the pitch.
Fundamental
soundThe lowest and usually strongest frequency in a tone — the pitch you actually hear.
seeWaveforms
G
Gain
soundAnother word for volume or level — how much a signal is turned up or down.
Generative
rhythmMusic made by a system of rules that plays itself, rather than a fixed pattern you program.
Glide
shapingA smooth slide in pitch from one note to the next, instead of jumping. Also called portamento.
seeAcid
H
Harmonic
soundA frequency at a whole-number multiple of the fundamental. The mix of harmonics gives a tone its character.
Hertz (Hz)
soundCycles per second — the unit of frequency. 440 Hz is the A that orchestras tune to.
Highpass filter
shapingA filter that passes high frequencies and turns down the lows — useful for thinning a sound out.
I
K
Karplus–Strong
synthesisA physical-modeling technique that makes a plucked string from a burst of noise circulating a tuned delay.
Key
soundThe root note and scale a piece is in. A shared key keeps every instrument sounding in tune together.
L
Leslie
effectA rotating speaker cabinet that gives organs their swirling, chorused motion. Spins slow or fast.
seeOrgan
LFO
shapingLow-Frequency Oscillator — a slow wave used to wobble something else, like pitch (vibrato) or volume (tremolo).
Lowpass filter
shapingThe most common filter: it passes low frequencies and turns down the highs, making a sound darker.
seeSubtractive
M
MIDI
gearA standard that lets instruments and software send notes and control messages to one another.
Modal synthesis
synthesisModelling the few ringing frequencies (modes) of a struck object like a bar or bell.
Modulation
shapingUsing one signal to change another — an LFO on pitch, an envelope on the filter, and so on.
Modulator
synthesisIn FM, the oscillator you don't hear directly — it bends the carrier's frequency to add harmonics.
seeFM
Monophonic
gearAble to play only one note at a time. Basslines and leads are often monophonic.
N
Noise
soundA random signal with no clear pitch. It's the raw material for percussion, wind and the pluck in a string.
O
Octave
soundA doubling (or halving) of frequency — the same note, an octave higher or lower.
Oscillator
synthesisThe part of a synth that generates the raw, repeating tone before anything shapes it.
Overtone
soundAnother word for a harmonic above the fundamental.
P
Partial
soundAny single frequency component in a sound, whether it lines up as a harmonic or not.
seeModal
PeriodicWave
gearThe Web Audio object that stores a custom single-cycle waveform, built from its harmonic recipe.
Physical modeling
synthesisSynthesis that simulates the physics of a real instrument rather than recording or filtering.
Pitch
soundHow high or low a note sounds. It's set by the frequency of the wave.
Polyphonic
gearAble to play several notes at once — needed for chords and pads.
Q
Quantize
rhythmSnapping notes onto the nearest beat, or the nearest note of the key, so nothing is out of time or out of tune.
R
Ratio
synthesisIn FM, the modulator's pitch compared to the carrier. Whole numbers ring like bells; fractions turn metallic.
seeFM
Resonance
shapingA boost in the frequencies right around a filter's cutoff, adding a whistle or squelch. High resonance is the acid sound.
S
Sawtooth
soundA bright, buzzy wave containing every harmonic — the richest raw material for subtractive synthesis.
seeWaveforms
Sequencer
rhythmA device that plays a pattern of notes in time, over and over, so you don't have to.
Sine
soundThe purest wave — a single frequency with no harmonics at all. Soft and hollow, like a whistle.
seeWaveforms
Square
soundA hollow, woody wave that contains only the odd harmonics. The classic chiptune tone.
seeWaveforms
Subtractive synthesis
synthesisStarting with a harmonically rich tone and carving harmonics away with a filter — the classic analog method.
Sustain
shapingThe volume a note holds at while the key stays down. It's a level, not a length of time.
T
Tempo
rhythmThe speed of the music, measured in beats per minute (BPM).
Timbre
soundThe character or colour of a sound — what makes a trumpet and a flute at the same pitch sound different.
Transient
soundThe short, loud burst at the very start of a sound, like the click of a pluck or the thud of a drum.
Tremolo
effectA wobble in volume driven by an LFO — the shimmer of a vibraphone or a Leslie.
Triangle
soundA mellow wave with only a few quiet harmonics — softer than a square, reedier than a sine.
seeWaveforms
U
V
Velocity
gearHow hard a key is struck, usually mapped to the volume or brightness of the note.
Vibrato
effectA gentle wobble in pitch, driven by an LFO.
Voice
gearOne note's worth of sound. A synth's polyphony is how many voices it can play at once.
W
Waveform
soundThe shape of one cycle of a sound wave. Its shape decides the harmonics, and so the timbre.
seeWaveforms
Wavetable
synthesisA set of single-cycle waveforms you scan through for shifting, evolving timbres.
Wet / dry
effectThe balance between the processed (wet) signal and the original (dry) one in an effect.