Synesthesia can be a very cool thing. In fact, it is several intersecting things: a literary device, a neurological phenomenon, a way that artists from Lorde to Kanye to Redlight visualise music on a rainbow spectrum.

It can take over seventy different forms. Grapheme-colour synesthesia causes letters and numbers to be speckled or blurred with colour, while chromesthesia (with which my musical mind is here concerned) leads to certain sounds, notes or keys being associated with colours. In 1842 Franz Liszt told the orchestra he was conducting to play “a little bluer”, while Scriabin insisted that D-major was a golden-brown key (The Stranglers may disagree). The phenomenon is still very much alive in the musical world today, and can sometimes be measured by neurological testing. At other times, people simply attest to associating certain sounds with a subconscious reflexive triggering of a colour or emotion.

Synesthesia, and its constituent sub-groupings, are even more fascinating if you look at the high incidence of talented artists that attest to experiencing it. Sibelius, for example, almost certainly had perfect pitch, helped by his association of note groupings with precise colours. In contrast, playing the cello when I was younger, the sound of the four strings ranged from a murky green to a murky blue: a fairly inaccurate sonic representation that probably explains both why I in no way have perfect pitch and my tendency to play out of tune.

In terms of the science, a doctor NME interviewed explained that synesthesia is basically a tangling up of the “cross-wires” of senses in your brain. MRI scans can show the rushing of blood to the visual, not just aural, parts of the brain when a subject listens to music. The results can be astonishing. Lorde told her Tumblr followers that her song 'Tennis Court' was originally “the worst textured tan colour”, but when lyrics and a pre-chorus were added it “changed to all these incredible greens overnight”. Devonté Hynes explained his score for the film Palo Alto to an NYU lecture hall by playing half an hour of different colours in a dark room and going through the emotions and feelings he associated with them.

It can be genetic, can skip generations, and typically on the ingestion of hallucinogenic drugs symptoms of synesthesia will appear within an hour. The research on it is extensive, but one thought is that it originates from childhood memories and associations of emotions and objects. While it can aid creativity and visualisation, some also attest to it becoming overwhelming in noisy places, like clubs, or in the middle of contrasting tones, such as in a choir.

The crossover between colours, emotions and music adds another fascinating dimension to chromesthesia, and is something that people who don’t experience it can be related to. As non-sensory feelings, emotions can more readily be associated with colour, but also with music. The result is a tantalisingly intangible sensation of blurred sensations, hues and visualisation when listening to music. Pharrell described Happy as triggering shades of mustard yellow in his mind, and, although I see no colours when listening to the song, the elation and euphoria of the track can surely only be yellow. Applying the same method to Vance Joy’s Riptide, I see pink.

Chromesthesia gets to the root of that immeasurable and infinitely complex issue of the way that music makes us feel. Music is difficult to capture in words  (as hard as armies of reviewers try) but taking a step back and thinking about it in terms of colour, or abstracted emotion, or whatever sensation it may be, can capitalise on the experience of listening to a piece. Whether you’re a synesthete or not, try it some time.