"What do you see when you hear this?"
Most people when listening to music can visualize something in their mind: maybe a landscape, a scene, a shape, an action...but what about a colour?
We usually find this term in dictionaries as "synesthesia," but since the word is Greek, and because I am also Greek, we respect the term's spelling and etymology by adding an a. Aesthesis means sense/perception and syn- is an additive preposition. While synaesthesia is a broad term that refers to the experience of one sensory or cognitive attribute invoking an experience in another unrelated sensory or cognitive pathway (for example, someone might see colors when they hear music or associate specific tastes with certain words) chromaesthesia is a specific subtype of synaesthesia where auditory stimuli, such as music or sound, lead to the experience of colors. Essentially, people with chromaesthesia "see" colors when they hear sounds. This phenomenon can be quite detailed, with different musical tones or instruments triggering specific colors. Again, the etymology originates from the Greek: chroma means colour.
There are many classical music composers that are said to be synaesthetic. Among others, here we find: Nikolai Rimsky-Korskakov (1844-1908), Alexander Scriabin (1872-1915), and Olivier Messiaen (1908-1992). A very interesting point is that different composers experienced synaesthesia in different ways. For example, Rimsky-Korsakov associated specific keys with certain colors, Messiaen associated specific pitches with colors, and Ravel correlated musical intervals with specific colors.
There are several studies that investigate the possibility of Robert Schumann having experienced analogous stimuli, which may have been induced by the heavy metals he was prescribed for his deteriorating mental health. However, the possibility of narcotics, arsenic, or metal-containing medications provoking chromaesthesia in musicians is outside the scope of this thesis.
Still, it is interesting to note that many synaesthetes (Scriabin, Messiaen) were stigmatized, and perceived as mad.
In Claude Samuel's "Music and Color", (a series of interviews with Olivier Messiaen), Messiaen "refuses" being synesthetic, though he references his synesthetic friend, the painter Blanc-Gatti, who experienced colors and shapes upon hearing music due to a neurological condition. Nonetheless, Messiaen later admits to a form of synesthetic experience, albeit more mental than physical. He describes an internal sensation where music and written scores evoke colors in his mind's eye, which he sometimes indicates in his compositions. Despite acknowledging this phenomenon, Messiaen acknowledges the difficulty of scientifically proving its existence. When questioned whether he genuinely perceives these colors or merely imagines them, Messiaen asserts that he inwardly sees them, distinct from imagination or a physical sensation—it's an internal reality for him. Furthermore, Messiaen elaborates on how incongruent lighting, such as violet light for a ballet set to Beethoven's G Major music, can cause discomfort, recalling an instance where he felt nauseated due to the discordance between the music and the lighting.⁜
In the above tabe we can see the colour sound correspondences proposed by the two Russian composers. As you can see, Rimsky-Korsakov refers to major keys whereas Scriabin to tonal pitches. As we will see later this is an example of a “trivial” analogous mapping.
We will talk thoroughly about Messiaen later. For now, we will dig into the current scientific knowledge on the subject. Apart from synaesthesia, which seems to be a specific neurobiological condition that only a certain amount of people possesses, -and which is triggered unconsciously, there is a wider scientific term that describes the connections between different stimuli that people are capable of doing consciously which is called Crossmodal Correspondence. While some researchers recognize the same mechanisms in the two, others treat them differently in an ontological way.
Until this point (February 2024) it is still not clear to me whether the term synaesthesia refers to a neurological condition which enables a different mechanism than a crossmodal correspondence or whether it is just a specific kind of CC. I deliberately didn’t want to dig into deeper cognitive and neurobiological processes since the length and duration of this thesis couldn’t support it. For example, even though perfect pitch is usually treated as a crossmodal correspondence phenomenon, in this paper you can read about the relationship between perfect pitch and synaesthesia. Also, according to Sagiv and Ward, ”Although the condition has been traditionally viewed as an anomaly (e.g., breakdown in modularity), it seems that at least some of the mechanisms underlying synaesthesia do reflect universal crossmodal mechanisms”.
The commonest forms of synaesthesia involve seeing colors when listening to sounds or words or reading letters or numbers. Synaesthesia is often described as a singular phenotype. However, convenient terminology and minimal definition might hide a variety of conditions with different etiologies and manifestations.⁕ We lack a clear understanding of what synaesthesia is, at either the psychophysical or the neurobiological level. The tendency to form apparently irrelevant, often highly consistent sensory associations is not restricted to synaesthetes.⁕ The level of analysis at which an inducer triggers a concurrent sensation can differ from one synaesthetic association to another, even within an individual.⁕
It is important to note that while crossmodal correspondences are fascinating and widely observed, they are not always consistent across individuals and cultures. Additionally, the mechanisms underlying these correspondences are still being researched and understood. They might be influenced by a combination of cultural factors, cognitive processes, and neural wiring. My understanding is that the substantial difference between synaesthesia and cross modal correspondence is that the first is an absolute event (always a one-to-one correspondence) whereas the latter even though systematic, is a relative event (includes the range of a scale). However, there is no evidence of any consistency of colour/music (note, chord, interval) association from one synaesthetic person to another (not even from one synaesthetic composer to another). Or at least I haven't come across such ground-breaking results.
And this is where it gets complicated. Since synaesthetes (they experience a priori an intrinsic connection between stimuli), and crossmodal models don't provide us with consistent results, there are big debates in literature. If several different notes are played simultaneously, as in a chord, most synaesthetes report experiencing several colours rather than a fusion of colours (See Cutsforth, 1925; Ginsberg, 1923; Myers, 1911; Riggs and Karwoski, 1934; Rogers, 1987; Whipple, 1900). This suggests that the critical auditory unit is at the level of the single note (or pitch) rather than a unit of perception operating across several notes (e.g., pitch groupings, interval values or melody).⁕ As we will see later, Messiaen describes his condition as operating through chords- not at the level of single or distinct pitches.
First and foremost, however, synaesthesia is still not taken seriously as a legitimate condition. Greta Berman in her article “Synesthesia and the Arts” is claiming that there is a misunderstanding, and that the term synaesthesia is used way more often metaphorically rather than accurately. Also, according to her, synaesthesia should be treated ontologically as a continuum, with a range that extends from pure synaesthetes to individuals with no crossmodal associations at all. It is a matter of ongoing debate to what extent such cross-modal correspondences share mechanisms with synaesthesia.⁕ So therefore, in the next section I will be elaborating on the different “nuances” of synaesthesia that I came across in the literatures.
Synaesthesia may be divided into two general, overlapping types. The first is ‘synaesthesia proper’, in which stimuli to one sensory input will also trigger sensations in one or more other sensory modes. The second form of synaesthesia, called ‘cognitive’ or ‘category synaesthesia’, involves synaesthetic additions to culture-bound cognitive categorizational systems. With this kind, sets of things which our individual cultures teach us to put together and categorize in a specific way – like letters, numbers, or people’s names – also get a sensory addition, such as a smell, colour, or flavour. The most common forms of cognitive synaesthesia involve such things as coloured written letter characters (graphemes), numbers, time units, and musical notes.
Synaesthesia has neurological components and is partly heritable. The percentage of the general human population which has synaesthesia varies with the roughly 60 types involved; estimates run from about 4 percent for basic types of cognitive synaesthesia (coloured letters or musical pitches) to about 0.03 percent for more common forms of synaesthesia proper (coloured musical sounds or coloured taste sensations) to less than 0.01 percent for people with rare or multiple forms of synaesthesia proper. Synaesthesia proper, also named ‘strong synaesthesia’, which is common to relatively few people, is frequently distinguished from ‘weak synaesthesia’, which is when we understand metaphors like a ‘warm’ or ‘sharp’ sound, or when we consider higher or louder sounds to be brighter, bigger, and more jagged, and lower or quieter sounds to be darker, smaller, and more round. These cross-modal analogies seem to be (nearly) universal. But a pitch-to-lightness correlation can also occur in connection with phenomena of strong synaesthesia, which thereby probably uses the same mechanisms as common cross-modal perception. What makes it even more complicated is that, in the artistic dimension, the term ‘synaesthesia’ is often used in a wider ‘synthetic’ sense, and generally refers to the Gesamtkunstwerk involving several senses.
Synaesthesia may influence composers and performers, but we still do not know in detail how it works. Synaesthetes, for example, those who see music as coloured, are not per se more creative in music or art. They have better access to certain associations, which may provide a source of motivation, but are not necessarily able to use them. ⁕