When E.S. hears tone intervals, the difference in pitch between two tones, she not only can see the musical notes as different colors but can taste the sounds.
"This is a special case of a musician who, when she hears tone intervals, she has a perception of a taste of a tone," said psychologist Michaela Esslen, of the University of Zurich in Switzerland.
"She doesn't imagine the taste, she really tastes it."
The case of E.S. reported in Nature is exceptional because seeing letters or digits in a certain color is more common in synaesthesia. It may also involve seeing a musical tone as a color.
But E.S. sees the colors and depending on the tone intervals a symphony could be bittersweet, salty, sour or creamy.
Psychologists Gian Beeli, Michaela Esslen and Lutz Jäncke tested "E.S.'s" synesthetic abilities by asking her to identify intervals while they stimulated her taste buds with four solutions (sweet, sour, salty, bitter). E.S. identified all the intervals correctly, but was faster in identification when the taste/interval configuration corresponded to her synaesthetic associations.
Figure 1 Mean reaction times in a gustatory Stroop task linking perception of tone intervals with different tastes for congruent-taste (grey), incongruent-taste (red) and no-taste (blue) conditions for synaesthete E.S. and for five non-synaesthetic musicians (controls). In the 'Taste' condition, musical intervals were presented while solutions of different taste (citric acid, 20 g litre-1; quinine, 60 mg litre-1; salt, 10 g litre-1; sucrose, 120 g litre-1) were delivered to the subject's tongue. The 'Conceptual' condition followed the same procedure, except that words describing the tastes, instead of the tastes themselves, were visually presented 2 s before the tone interval. Non-parametric randomization tests were used for statistical comparison. For E.S., all statistical comparisons in the taste condition were associated with P values of less than 0.01 (*P<0.05,>**P<0.01,>***P<0.001).>
What I would find interesting is what E.S.'s instrument is. Does she have reeds in her mouth, or a metal mouthpiece pressed to her lips, or is her instrument oral-free?
G. Beeli, M. Esslen & L. Jäncke. "Synaesthesia: When coloured sounds taste sweet." Nature 434, 38 (March 2005); doi:10.1038/434038a