The color of music: Emotion-mediated associations to Bach’s Well-tempered Clavier.

Associations between music and color, and cross-modal associations in general, have been understood in a variety of ways. One view is that, because we experience the world through multiple sensory modalities simultaneously, integrating these signals provides us with richer and more precise information on which to act (Parise & Spence, 2013; Spence, 2011). Cross-modal associations, for example, between the color of a fruit and whether or not it tastes ripe, are normal and adaptive for integrating information across the senses. Three types of cross-modal associations that have been identified are structural correspondences (originating in the neural processing), statistical correspondences (reflecting regularities in the world), and semantically (primarily verbally) mediated correspondences (Spence, 2011).Walker and colleagues (Walker & Smith, 1984; Walker, Walker, & Francis, 2012) have proposed a system of amodal, conceptual terms that apply across sensory modalities to account for cross-modal associations. These draw on basic features of bodily actions, gestures, and vocalizations. For example, common to hearing and sight are fast versus slow, high versus low, bright versus dark, and small versus large. Such cross-sensory correspondences may be bidirectional and symmetrical, or asymmetrical with the association in one direction being stronger than in the other, or even unidirectional. Hearing a high sound might lead one to expect that a small object is the source, but a small object would not necessarily lead one to expect a high sound. Walker (2016) describes how the theory might apply to music, going beyond associations to simple tones varying in pitch height, loudness, and/or timbre, to possible factors operating at compositional levels of melody and tempo.One issue that arises in the literature on cross-modal associations is what the relationship is between these associations and the phenomenon of synesthesia, in which a trigger stimulus ("inducer") causes automatic, perception-like experiences ("concurrent") in a different modality. Although cross-modal associations have been found to be consistent across individuals, the focus in research on synesthesia tends to be on individuals under the assumption that the particular correspondences would be idiosyncratic. Hundreds of different types of synesthesia have been identified, with a history of scientific reports going back to the 1800s (Galton, 1883; see Jewanski, 2013; Ward, 2013 for reviews). Recently, it has been suggested that synesthesia may be subject to the same rules that govern normal patterns of cross-modal associations, differing mainly in its automaticity but less in its phenomenology (Marks, 2013; Simner, 2013; but see Spence, 2011).Marks (1975) reviewed >100 reports of auditory-visual synesthesia, many of which involved music. He found that some of the associations are regular, systematic, and consistent across individuals. Specifically, there were correlations between auditory pitch and visual brightness (the higher the brighter, and in some studies more yellow), and pitch and visual size (larger with lower), and loudness and visual size and brightness (larger and brighter with louder). Marks described devices invented to present colors to accompany music, such as an organ built by Scriabin that mapped tones and colors so that, for example, C was accompanied by red, and D accompanied by yellow. Associations between musical notes and/or keys and colors are quite common in synesthetes and a case study demonstrated stability over time (Carroll & Greenberg, 1961). However, as noted by Marks, the specific mappings tend to vary across individuals, so that C might be red to one synesthete and white to another. Other, also idiosyncratic, associations have been reported between color and musical instruments, such as trumpet and scarlet, and flute and blue, and the music of particular composers, such as Chopin and purple, Mozart and green, or specific works by composers. …