GLOSSARY
Sound and vision, defined.
169 working definitions across synesthesia science, audio analysis, live visuals, and visual music history. Written for people who make things.
Synesthesia and perception
Acquired synesthesia
Synesthesia-like experiences that begin after brain injury, sensory loss, or illness rather than in childhood.
ASMR
A tingling, calming sensation triggered in some people by soft sounds such as whispering and tapping. Autonomous sensory meridian response.
Associator synesthete
A synesthete who experiences concurrents in the mind's eye rather than projected into external space.
Audiovisual integration
The brain's merging of sound and vision into one percept, weighting each channel by reliability and timing.
Auditory-tactile synesthesia
A form of synesthesia in which sounds produce physical sensations on the body, such as tingling, pressure, or texture.
Bouba-kiki effect
The near-universal tendency to match the word bouba with rounded shapes and kiki with spiky ones, showing sound-shape mapping in everyone.
Chromesthesia
Sound-to-color synesthesia: hearing music or other sound produces involuntary, consistent experiences of color and shape.
Colored hearing
The historical term for hearing-triggered color experiences, now usually called chromesthesia or sound-to-color synesthesia.
Concurrent
In synesthesia research, the experience triggered by the inducer, such as the color that arrives when a sound is heard.
Cross-activation theory
The hypothesis that synesthesia arises from extra anatomical connections between adjacent brain regions, such as the grapheme and color areas.
Cross-modal correspondence
Reliable associations between senses that most people share, such as matching high pitches with bright, small, fast things.
Developmental synesthesia
The common, lifelong form of synesthesia that emerges in childhood without injury or drugs, and tends to run in families.
Disinhibited feedback
The hypothesis that synesthesia arises when normal feedback between senses, present in everyone, escapes its usual inhibition.
Drug-induced synesthesia
Temporary cross-sensory experiences under psychedelics such as LSD or psilocybin, where sounds can produce visual effects.
Emotion-color synesthesia
A form of synesthesia in which emotions, or people carrying them, are perceived with consistent colors, sometimes described as auras.
Grapheme-color synesthesia
The most studied form of synesthesia, in which letters and numerals are perceived as having consistent, involuntary colors.
Ideasthesia
A framing of synesthesia in which concepts, not raw sensations, trigger the experiences: the meaning of the inducer does the work.
Inducer
In synesthesia research, the stimulus that triggers the synesthetic experience, such as the sound that produces a color.
Lexical-gustatory synesthesia
A rare form of synesthesia in which words trigger involuntary and specific taste experiences.
McGurk effect
An illusion where seeing a speaker's lips changes what sound is heard: proof that hearing and vision merge before awareness.
Mirror-touch synesthesia
A form of synesthesia in which seeing another person being touched produces a felt touch sensation on the observer's own body.
Misophonia
A condition in which specific ordinary sounds, often chewing or breathing, trigger immediate strong emotional reactions.
Music-color synesthesia
Chromesthesia triggered specifically by musical structure, where keys, chords, timbres, or pitches carry consistent colors.
Number form
A stable mental map in which numbers occupy fixed spatial positions, first documented by Francis Galton in 1880.
Odor-color synesthesia
A form of synesthesia in which smells trigger consistent color experiences.
Ordinal linguistic personification
A form of synesthesia in which ordered units like numbers, letters, and weekdays have consistent personalities and genders.
Pain-color synesthesia
A form of synesthesia in which pain is experienced with consistent visual qualities such as color and shape.
Phosphene
A sensation of light without light entering the eye, produced by pressure, electrical stimulation, or spontaneous activity in the visual system.
Photism
An involuntary visual sensation triggered by a non-visual stimulus, usually sound: the color or shape a synesthete sees when hearing music.
Projector synesthete
A synesthete who experiences concurrents out in external space, such as seeing colors floating near the sound source or on the page.
Sensory substitution
Technology that delivers one sense's information through another, such as devices that translate camera images into soundscapes.
Spatial sequence synesthesia
A form of synesthesia in which ordered sequences such as months, weekdays, or numbers occupy fixed positions in space around the person.
Synesthesia
A stable trait of perception in which stimulating one sense automatically triggers an experience in another, such as hearing a sound and seeing a color.
Synesthesia battery
A standardized set of tests for verifying synesthesia, combining consistency measures with speeded classification tasks.
Synesthete
A person with synesthesia: someone for whom one sense reliably and involuntarily triggers another, such as seeing colors when hearing music.
Test-retest consistency
The standard method for verifying synesthesia: genuine synesthetic pairings stay stable when retested months or years apart.
Ticker-tape synesthesia
A form of synesthesia in which heard speech appears as visible scrolling text, like subtitles generated by the mind.
Time-space synesthesia
A form of synesthesia in which units of time occupy definite locations in space, such as a year arranged as a ring around the body.
Touch-color synesthesia
A form of synesthesia in which tactile sensations such as texture and pressure trigger consistent colors.
Visually evoked auditory response
Hearing faint sounds from silent moving images, such as flashing GIFs that seem to thud. A common, mild form of cross-sensory perception.
Audio analysis
A-weighting (dBA)
A filter applied to sound level measurements that discounts frequencies the ear hears poorly, producing the dBA figures used in noise limits.
Amplitude
The size of an audio signal's swing, the physical quantity underlying loudness.
Attack time
How quickly a sound or a processor reaches full level from silence: the leading edge of the envelope.
Audio analysis
Extracting structured information from sound in real time: levels, bands, onsets, pitch, the input layer of every audio-reactive system.
Audio buffer
The block of samples audio systems process at a time; its size trades processing safety against latency.
Audio latency
The delay between a sound occurring and the system responding to it, the budget every real-time audio process spends.
Band-pass filter
A filter that passes one region of the spectrum and attenuates both above and below it.
Beat detection
Inferring the musical pulse from audio: finding the tempo and predicting when the next beat lands.
Chroma features
A twelve-value summary of audio energy per pitch class, showing harmony independent of octave.
Clipping
Distortion produced when a signal exceeds the maximum level a system can carry and its peaks are flattened at the ceiling.
Decibel (dB)
The logarithmic unit of audio level, matching how hearing perceives loudness ratios rather than absolute amounts.
Envelope
The overall shape of a sound's level over time: how it attacks, sustains, and fades, apart from its pitch or timbre.
Envelope follower
A circuit or algorithm that outputs the smoothed level of a signal in real time, turning audio into a usable control signal.
FFT (fast Fourier transform)
The algorithm that converts audio from a waveform over time into a spectrum of frequencies, the basis of nearly all audio-reactive visuals.
FFT bin
One slot of an FFT's output, holding the energy found in one narrow band of frequencies.
Frequency bands
Named regions of the spectrum, such as sub-bass, mids, and highs, used to route different parts of the music to different behavior.
Frequency spectrum
The distribution of a sound's energy across frequencies at a moment, from sub-bass rumble to airy highs.
Headroom
The space between a signal's level and the ceiling of the system carrying it, the margin that keeps peaks clean.
High-pass filter
A filter that lets frequencies above its cutoff through and attenuates everything below, the standard tool for removing rumble and mud.
Lissajous curve
The figure drawn when two signals drive the two axes of a display, looping into knots set by their frequency ratio.
Low-pass filter
A filter that lets frequencies below a cutoff through and attenuates everything above it.
LUFS
Loudness Units relative to Full Scale: the broadcast-standard measure of perceived loudness over time, used by streaming platforms.
Nyquist frequency
Half the sample rate: the highest frequency digital audio can represent without corruption.
Onset detection
Finding the exact moments when new sonic events begin, such as drum hits and note attacks, from the audio signal itself.
Oscilloscope
An instrument that draws voltage over time, showing audio as a live moving waveform.
Peak hold
A metering behavior where the highest recent level stays marked while the live level moves below it.
Pitch detection
Estimating the fundamental frequency of what is playing: the note, extracted from the signal.
RMS
Root mean square: the running average energy of a signal, matching perceived loudness better than instantaneous peaks.
Sample rate
How many times per second digital audio measures the waveform, setting the highest frequency that can be captured.
Sidechain
Routing one signal to control a processor acting on another, the mechanism behind pumping compression and ducking.
Spectral centroid
The center of mass of a sound's spectrum, the standard computational measure of brightness.
Spectral flux
How much the spectrum changes from one instant to the next, the standard fuel for onset detection.
Spectrogram
A rendering of sound as an image: time runs along one axis, frequency along the other, and brightness shows energy.
Stereo field
The left-right space of a mix: where sounds sit between the speakers and how wide the whole image feels.
Sub-bass
The lowest useful band of the spectrum, roughly 20 to 60 Hz, felt in the body as much as heard.
Transient
The brief, sharp burst of energy at the start of a sound, carrying its impact and much of its identity.
Vectorscope
A meter that plots left against right channel, drawing the stereo relationship as a shape: tall for mono, wide for out-of-phase.
VU meter
The classic averaging level meter with a swinging needle, standardized in 1942 and deliberately slow to match perceived loudness.
Waveform
The shape of a sound drawn as amplitude over time, the standard visual representation of raw audio.
Window function
The taper applied to a chunk of audio before an FFT, trading off frequency precision against leakage artifacts.
Live visuals and VJ craft
Ableton Link
Ableton's network protocol for sharing tempo and phase between apps and machines, keeping visual software in step with the beat.
Alpha channel
The transparency layer of an image: per-pixel opacity that lets layers composite cleanly.
Aspect ratio
The width-to-height proportion of the image: 16:9 screens, 9:16 phones, 1:1 feeds, and the odd shapes of LED walls.
Audio-reactive visuals
Visuals driven directly by live analysis of sound, so the image moves because the music did.
Blend modes
The arithmetic for combining layers: add, multiply, screen, and their kin, each a different way for images to interact.
Bloom
A post-processing glow where bright areas bleed soft light into their surroundings, reading as intensity and atmosphere.
Boids
The three-rule flocking algorithm from 1986: separation, alignment, cohesion, from which lifelike swarms emerge with no leader.
Cellular automata
Grids of cells updating by simple neighbor rules, from which complex, lifelike pattern emerges: Conway's Game of Life is the famous one.
Chroma key
Removing a color, classically green, from video so another image shows through: the green screen technique.
Chromatic aberration
A lens flaw where color channels focus differently, borrowed by digital visuals as fringing that reads as impact or unreality.
Cymatics
Making sound visible through physical matter: sand, water, or particles arranging into geometric patterns on a vibrating surface.
Datamoshing
Corrupting compressed video so motion from one shot smears the pixels of another: the melting, ghosting signature of glitch video.
Dithering
Adding engineered noise so limited color depth renders smooth gradients instead of visible bands.
DMX
The standard control protocol of stage lighting: 512-channel universes addressing dimmers, movers, and LEDs, now often carried over Ethernet as Art-Net or sACN.
Edge blending
Overlapping multiple projectors and fading their shared regions so several images fuse into one wide picture with no visible seams.
Film grain
Fine animated noise laid over the image, borrowed from photochemical film to add texture and hide digital flatness.
Flow field
A grid of directions that steers particles or strokes, producing coherent swirling motion from simple rules.
Fluid simulation
Real-time computation of fluid physics, producing genuine swirling, curling ink-and-smoke behavior on the GPU.
Fragment shader
The GPU program that computes the color of each pixel, where most of the look of real-time visuals is authored.
Frame rate
How many images per second a system renders or displays, setting the smoothness and responsiveness of motion.
Generative visuals
Visuals produced by algorithms rather than played back from footage, unique each run and steerable by rules, randomness, or sound.
Glitch art
The aesthetic of digital failure used on purpose: corrupted files, broken codecs, and torn signals as visual material.
GLSL
The OpenGL Shading Language: the C-like language shaders are written in for OpenGL and WebGL.
HAP codec
A video codec built for VJ playback: decoded by the GPU, so many clips scrub and layer smoothly at once.
ISF (Interactive Shader Format)
A standard for packaging GLSL shaders with a control interface, so effects and generators travel between VJ apps.
Jitter
Max/MSP's video and 3D graphics system: matrices and GPU objects patched together for real-time visuals.
Kaleidoscope effect
Mirroring the image into radial segments, turning any motion into symmetric mandala patterns.
Keystone correction
Compensating for a projector aimed off-perpendicular, squaring the trapezoid it would otherwise draw.
L-system
A string-rewriting grammar that grows branching structures: the standard way computers draw plants, from ferns to whole forests.
LED wall
A display built from LED panels, the dominant large-format stage canvas, defined by its pixel pitch and processor.
Lumens
The measure of a projector's light output, and the currency that decides whether an image survives stage lighting.
Max for Live
The environment that runs Max/MSP patches as devices inside Ableton Live, the platform visual and utility devices are built on.
Media server
The specialized playback machine of large shows: many video outputs, warping, timecode sync, and show control in one system.
Metaballs
Blobs defined by overlapping influence fields that merge and split like mercury: the classic organic-liquid effect.
MIDI mapping
Binding hardware knobs, pads, and faders to software parameters, the standard way VJs perform their rigs.
MilkDrop
The influential music visualizer from Winamp, whose beat-reactive preset system still defines a whole aesthetic of psychedelic visuals.
Moiré pattern
The large interference pattern created when two fine regular patterns overlap: screen-door shimmer as artifact, or as instrument.
NDI
Network Device Interface: video sent over ordinary Ethernet networks, replacing capture cards and HDMI runs in many rigs.
OSC (Open Sound Control)
A network protocol for expressive control messages between music and visual software, the higher-resolution successor to MIDI in rigs.
Particle system
A rendering technique animating thousands of small elements under shared rules, used for swarms, sparks, smoke, and audio-driven bursts.
Perlin noise
Smooth, natural-looking randomness: the gradient noise function behind most organic motion and texture in computer graphics.
Persistence of vision
The eye's brief retention of an image after it disappears, the perceptual glue behind spinning-LED displays, light painting, and every screen you watch.
Phyllotaxis
The spiral arrangement plants use to pack seeds and leaves, built on the golden angle: the sunflower pattern, and a generative staple.
Post-processing
Effects applied to the finished frame each render, such as bloom, grain, and grading: the look layer of real-time visuals.
Projection mapping
Warping projected video to fit real objects and architecture, so surfaces appear to move, break, or glow.
Raymarching
Rendering 3D scenes by stepping rays through space against a distance function, the technique behind most single-shader 3D worlds.
Reaction-diffusion
A simulation of two interacting chemicals that spontaneously grows organic patterns: spots, stripes, corals, and labyrinths.
Render pipeline
The ordered stages that turn scene data into the final frame: geometry, shading, effects, output, repeated every frame.
Resolution
The pixel dimensions of the rendered image and of the display it feeds, from 1080p club projectors to dense LED walls.
Scanlines
The horizontal line structure of CRT screens, now a shader effect that stamps footage as vintage, broadcast, or machine-made.
Shader
A small program that runs on the GPU for every pixel or vertex, the engine of modern real-time visuals.
Signed distance field (SDF)
A function giving the distance from any point to the nearest surface, negative inside: the mathematical clay of shader-based 3D and crisp text rendering.
SMPTE timecode
The broadcast-standard clock signal (hours:minutes:seconds:frames) that locks video, lighting, and playback systems together in shows.
Spout
The Windows equivalent of Syphon: GPU-level video sharing between applications on one machine.
Strange attractor
The never-repeating orbit a chaotic system settles into, drawn in phase space: chaos with a shape.
Syphon
The macOS framework that shares live video between applications on the same machine with almost no cost.
Throw distance
How far a projector must sit from the surface to fill it, set by the lens's throw ratio.
Video feedback
Feeding a camera or renderer its own output, producing tunnels, trails, and endlessly recursive imagery.
Video processor
The hardware between sources and an LED wall, scaling and mapping incoming video onto the panel grid.
VJ
A visual jockey: the performer who mixes and manipulates visuals live alongside music.
VJ loop
A short video clip made to repeat without a visible join, the basic content unit of clip-based VJ performance.
VJing
The live performance of visuals: mixing clips, effects, and generative sources in real time with music.
Voronoi diagram
Space divided by nearest neighbor: every point colored by which seed it is closest to, yielding the cell pattern of cracked mud, foam, and giraffe skin.
WebGL
The browser's GPU graphics API, making every browser window a real-time visuals surface without installation.
Visual music history
Absolute film
The 1920s German movement of pure abstract cinema: geometric forms moving in musical rhythm, film as composition rather than photography.
Clavier a lumieres
The keyboard of lights Scriabin scored in Prometheus: The Poem of Fire (1910), a written color part inside a symphony.
Clavilux
Thomas Wilfred's light-performance instruments, first shown in 1922: projectors and controls for playing silent compositions of moving color.
Color organ
An instrument that performs light as music does sound, from 18th-century harpsichords with colored papers to the filter-driven lamp boxes of the disco era.
Demoscene
The computer subculture of real-time audiovisual demos, where coders push hardware to produce synchronized music and visuals from pure code.
iTunes visualizer
The visualizer generations bundled with iTunes, from psychedelic particle flows to 2008's Magnetosphere, mainstream ambient visuals for a decade.
John Whitney
The father of computer motion graphics (1917-1995), whose mechanically and digitally computed films sought a shared harmony of music and motion.
Joshua Light Show
The celebrated liquid light crew led by Joshua White, house light show of New York's Fillmore East from 1968.
Kandinsky and music
The painter's program of building abstraction on musical principles, informed by his reported synesthetic experience of sound as color.
Laser show
Performance graphics drawn by steered laser beams: vector imagery and aerial effects, a fixture of music spectacle since the 1970s.
Light organ
The consumer sound-to-light box of the 1970s: filter circuits flashing colored lamps with the bass, mids, and treble of whatever played.
Liquid light show
The 1960s psychedelic projection technique: oils, dyes, and water manipulated live on overhead projectors behind bands.
Lumia
Thomas Wilfred's name for the art of light itself: slow, silent compositions of drifting luminous form, performed on his Clavilux instruments.
Lumigraph
Oskar Fischinger's performed light instrument (c. 1950): pressing a rubberized screen into a plane of colored light to paint moving forms live.
Mary Ellen Bute
American pioneer (1906-1983) of abstract film set to music, and among the first to make images electronically with an oscilloscope.
Newton's color-music circle
Newton's division of the spectrum into seven colors matched to the seven notes of a scale, the founding analogy of color music.
Norman McLaren
The Scottish-Canadian filmmaker (1914-1987) who drew both image and sound directly onto film, fusing music and visuals at the physical level.
Ocular harpsichord
Louis Bertrand Castel's 1720s proposal for a harpsichord that would present colors with its notes, the first designed color-music instrument.
Oskar Fischinger
The German-American animator (1900-1967) whose hand-drawn abstractions synchronized to music defined the look of visual music on film.
Prometheus: The Poem of Fire
Scriabin's 1910 orchestral work scored with a part for light, the landmark attempt to compose color into symphonic music.
Rimington's color organ
The 1893 projection instrument by Alexander Wallace Rimington that gave the color organ its name and its first concert performances.
Scriabin's color system
The composer's mapping of musical keys to colors, arranged around the circle of fifths, used in his light-scored works.
Son et lumiere
Sound and light: the postwar French format of nighttime shows washing architecture with synchronized light, narration, and music.
Visual music
The art of structuring image in time the way music structures sound: abstraction, rhythm, and composition without narrative.
Winamp AVS
Advanced Visualization Studio: Winamp's scriptable visualizer (1999) whose preset culture seeded modern audio-reactive graphics.