Synesthesia in music is an involuntary neurological phenomenon where hearing music triggers experiences in another sense, most commonly seeing colors. A person with this type of synesthesia might perceive a C major chord as bright yellow or experience a bass note as a deep purple wash across their visual field. It’s not imagination or metaphor. The colors, shapes, or textures appear automatically and consistently every time the same musical element is heard.
How Musical Synesthesia Works in the Brain
The most common form of musical synesthesia is called chromesthesia, or sound-to-color synesthesia. When a person with chromesthesia hears a note, chord, or timbre, their brain simultaneously activates visual processing areas that wouldn’t normally respond to sound alone. Brain imaging studies show that synesthetes have stronger connections inside and between sensory regions compared to non-synesthetes, who instead activate frontal and parietal areas when processing the same input.
There are two leading models for how this happens. One proposes that auditory signals travel through unusually dense horizontal connections directly to the color-processing area of the visual cortex, triggering color perception without any conscious effort. The other suggests a higher-order brain region that normally keeps auditory and visual processing separate fails to fully inhibit the cross-talk, allowing sound information to “leak” into visual areas. Both models point to the same basic reality: the brain’s sensory boundaries are more porous in people with synesthesia.
Color isn’t the only possible secondary experience. Some musical synesthetes perceive textures, spatial patterns, or even tastes when they hear music. But sound-to-color is by far the most studied and most commonly reported form.
Projectors Versus Associators
Not everyone with musical synesthesia experiences it the same way. Researchers distinguish between two subtypes: projectors and associators. Projectors see colors in their external visual field, as if the color occupies physical space around them or emanates from the source of the sound. Associators experience the colors internally, in what they describe as their “mind’s eye,” more like a vivid mental image than something overlaid on the world.
Both types are consistent and automatic. The distinction is about where the experience feels like it’s happening, not whether it’s real. A projector might describe a violin solo as painting streaks of gold across the room. An associator hearing the same solo would “see” the gold internally, as clearly and reliably, but without it appearing to exist in space.
What Musicians With Synesthesia Actually Describe
Several well-known musicians have spoken publicly about their synesthetic experiences, and their descriptions help illustrate how varied and vivid the phenomenon can be.
Pharrell Williams has described synesthesia as essential to how he works: “It’s the only way that I can identify what something sounds like. I know when something is in key because it either matches the same color or it doesn’t.” For him, color acts as a tuning system. Billie Eilish has said that her music videos, artwork, and live shows are all driven by synesthesia: “All the colors for each song, it’s because those are the colors for those songs specifically.” Lorde has described how synesthesia shaped production decisions, recalling that an early version of “Tennis Court” produced “the worst textured tan colour” that made her feel sick, and that the song only clicked when a new prechorus shifted it to “incredible greens.”
The phenomenon isn’t new. In the 19th century, composer Franz Liszt reportedly baffled orchestra musicians by calling out color instructions during rehearsals: “O please, gentlemen, a little bluer, if you please! This tone type requires it!” Stevie Wonder, who has been blind since shortly after birth, has described sensing color in his mind as he plays and listens to music.
How Common It Is Among Musicians
Sound-to-color synesthesia occurs in roughly 0.3% to 1.3% of the general population. Among musicians, the numbers jump to between 1.3% and 7.3%, depending on how strict the diagnostic threshold is. That makes musicians about four times more likely to have sound-to-color synesthesia than non-musicians.
Whether music attracts people who already have synesthesia or whether intensive musical training somehow strengthens latent cross-sensory connections is still an open question. But the statistical link is strong enough that synesthesia appears to be a meaningful part of how some musicians perceive and create.
Genetics and Who Develops It
Most people with synesthesia have had it for as long as they can remember. It runs in families, and a large twin study estimated that genetics account for about 46% of the variation in synesthesia traits, with the remaining 54% attributed to individual environmental factors (not shared family environment, but unique experiences). Molecular studies have identified genes involved in how nerve fibers grow and form connections, which aligns with the brain imaging evidence of extra wiring between sensory areas.
In rare cases, synesthesia can also be acquired later in life. One documented case involved a 66-year-old musician who developed sound-to-color synesthesia after a traumatic brain injury. He began “seeing” musical notation and could visually identify chord structures of music he heard, both entirely new experiences for him. His case also came with a notable boost in creativity. Psychedelic drugs can produce temporary synesthetic experiences as well, though these typically don’t persist once the substance clears the system.
Effects on Memory and Creativity
People with synesthesia tend to have measurable advantages in certain cognitive areas. Studies have found that synesthetes can recall more words from a memorized list than non-synesthetes, remembering up to three additional words from a 15-word list in delayed recall tests. This advantage likely comes from having an extra sensory “tag” attached to each piece of information. If a word triggers both a sound and a color, there are two pathways to retrieve it later.
The memory benefits aren’t universal, though. On tasks like digit span (repeating back strings of numbers), synesthetes perform about the same as everyone else. The boost seems specific to situations where the synesthetic associations can serve as an additional encoding layer.
Creativity is where the differences are most striking. One study found that roughly 24% of self-referred synesthetes held artistic occupations, compared to just 2% of a control group. Synesthetes scored notably higher on convergent thinking, the ability to connect seemingly unrelated ideas into a single solution. They also scored higher on measures of openness to experience, mental imagery use, and a trait called absorption, which reflects the tendency to become deeply immersed in sensory or imaginative experiences. On divergent thinking tasks, like generating unusual uses for everyday objects, the differences were smaller and less consistent.
How Synesthesia Is Verified
Because synesthesia is a subjective experience, researchers needed a way to distinguish genuine synesthetes from people who simply imagine or associate colors loosely. The standard tool is the Synesthesia Battery, a freely available online test. For sound-to-color synesthesia, it works by presenting the same sounds multiple times in randomized order and asking the participant to choose matching colors from a palette of 16.7 million options.
The key measure is consistency. A genuine synesthete will pick nearly identical colors for the same sound every time, even across sessions separated by weeks or months. Scores are calculated on a scale where 0.0 means perfect consistency. Scores below 1.0 are classified as synesthetic, while non-synesthetes typically score around 2.0 or higher, reflecting much more variation in their color choices. This consistency is the hallmark that separates synesthesia from ordinary association or imagination. You might casually think of a trumpet as “brassy” or “warm,” but a synesthete sees a specific shade of orange for that trumpet every single time, without effort or deliberation.