But I understand that inner knowing, as well. Sometimes I don't "see" my synesthetic associations out in front of me or in my mind's eye, but rather "know" inside, that, for example, Tuesday is golden. I wanted to share so he wouldn't feel so alone or strange or on the spot. So I told him about my inner golden Tuesday and he laughed. "That's just because Monday is over." We were both laughing then.

"If I play a B flat on the G string, I would say that the color for me is probably deep forest green. And if I play an A on the E string, that would be red. If I play the next B, if I look at it right now I would say that it's yellow. The bright colors are the upper strings of the violin -- for me I associate it with bright colors of the spectrum." To share one's personal associations is currency in the synesthesia world and I am so grateful to know his personal palette. We are not all the same. I thought how my musical notes are simply colored by the letters representing them and don't have a separate rainbow like his. There is great diversity within the synesthesia realm.

In grouping bright or dark colors into high or low octaves, Mr. Perlman is like many people. I remember reading how a mild degree of synesthesia is very common according to Alan D. Baddelay in the book, Essentials of Human Memory. "Most people have a slight tendency to associate high-pitched sounds with bright colors and low-pitched sounds with more somber hues,'' he writes. And Bulat M. Galeyev noted it in his paper The Nature and Functions of Synesthesia in Music for Leonardo, the MIT journal: "C. Debussy relied upon the effect of that common synesthesia when he transposed the familiar motif in The Lullaby of the Elephant Call into the lowest register." However in linking specific colors to the notes in those groups, the maestro is unique.

Mr. Perlman explained that "One of the languages that one uses in teaching in describing what is missing from a [musical] phrase is, ‘You need to give some color to these phrases. That phrase didn't have enough color. Or change colors.' "He says that has to do with variety and that shading is an even more precise description -- certain colors can be more pastel, more bold, and so on. And that's very much associated with the sound that one produces, he explained. When he teaches at his prestigious camp for young people on Shelter Island he uses that analogy to describe what he wants. I realize it is common for musicians or even writers to talk about coloring a phrase. And people without synesthesia can understand the sentiment of various colors: paint the town red, in a blue mood, green with envy, black-hearted, purple with rage. Iconic writers from Emily Dickinson in Dying to Pablo Neruda in Poetry have used cross-sensory pairings as metaphor. And yet, synesthesia is that and more.

Dr. Oliver Sacks wrote of synesthesia and music in Musicophilia: Tales of Music and the Brain. "For most of us, the association of color and music is at the level of metaphor. ‘Like' and ‘as if' are the hallmarks of such metaphors. But for some people one sensory experience may instantly and automatically provoke another. For a true synesthete, there is no ‘as if' - simply an instant conjoining of sensations."

Dr. Sacks gets at the heart of the matter here. If I wanted to be metaphorical about Mr. Perlman's friend Yo-Yo Ma playing Bach's Prelude in G from Cello Suite #1, I would pick something lovely, such as it like the sound made by spring's first flowers emerging from under the last winter snow. In truth, though I love this piece and it makes me want to wax poetic as much as anyone, it is for me a less bucolic image of ribbons of coffee coming from his strings in the shape of those glossy Christmas peppermints that fold back on themselves like waves. It is not a metaphor to me, it is a real image. It's that and more. I'd really have to create it in molten, moving glass to give you a full sense of its dimension and sheen and beauty. 

But there is overlap between synesthetes themselves and metaphor. Dr. V.S. Ramachandran of the University of California at San Diego says that synesthesia is as high as eight times more common in creative people: poets, writers, musicians and artists of various kinds. "If you assume that there is greater cross-wiring and concepts are located in different parts of the brain, then it's going to create a greater propensity toward metaphorical thinking and creativity in people with synesthesia," he said in a TED lecture. He told me he believes the gene for synesthesia is actually expressed more diffusely throughout synesthetes' brains than just the known hotspots, providing pathways that create an environment for linking seemingly unrelated things. If connected neurons live in concentrated groups in some minds, the synesthesia brain may have a wider fishing net of interconnected nerves.

So Mr. Perlman has both literal synesthesia and a propensity for metaphor -- they seem to go together. And he said the young people - none of whom are synesthetes -- get it when he goes at music metaphorically. "I think that people get it in their own way. Everybody has a particular association with what you describe. Teaching, and it's very interesting because it is even more obvious when teaching the voice, is unless you are really in the person's body, the way you describe what you want is extremely important. So language is really very, very important as to how you can say something to somebody and have them translate it in a particular way."

He doesn't remember how old he was when he noticed his particular note to color associations. "I just felt that it was an obvious thing... because it's not like it's a gift that you can do tricks with or something like that. It's just something that you can associate with."

But I think you can do tricks with it. I wanted to show him the beauty of the trait to repay him in some small way. So I asked if it comes in handy as a mnemonic device given the huge amount of memorization he must do for his profession. For example, I ask him if he ever plays a piece of music and knows some red is coming up ahead in the song? And he says yes, that is the case!

Mr. Perlman had another revelation now that he was thinking about the hard-to-verbalize experience. I felt a comfort level growing between us as he revealed more of the impressions he gets when bowing his priceless 1714 Soil Stradivarius. "Besides colors I see shapes," he admitted. "Each note has a shape. I would say that if you play a D on the G string, for me that's round. But if you play an A on an E string for me, that's much more flat, the shape of it. I hope not the intonation, but the shape of it."

Mr. Perlman said music is shape, it's feel and it's color -- it's everything. "It's everything that you can use to describe the note. The important thing is the way that it's helpful in identifying the sound, and in sort of being involved with the sound, to actually have a feel about what the sound does to you. It does to you with shapes, it does to you with intensity, it does to you with colors. And then you can really associate yourself with the sound. But sound, when you hear anybody play an instrument or sing, the first thing that you hear, the first thing that you're struck by, is a sound. You're struck by the sound without even wanting to be struck by the sound. It's just there; it's the first thing that meets your ear."