Hume wondered whether one can imagine a color that one has never encountered. One day in 1964, I constructed a sort of pharmacological mountain, and at its peak, I said, "I want to see indigo, now!" As if thrown by a paintbrush, a huge, trembling drop of purest indigo appeared on the wall -- the color of heaven. For months after that, I kept looking for that color. It was like the lost chord.Link
Then I went to a concert at the Metropolitan Museum of Art. In the first half, they played the Monteverdi Vespers, and I was transported. I felt a river of music 400 years long running from Monteverdi's mind into mine. Wandering around during the interval, I saw some lapis lazuli snuffboxes that were that same wonderful indigo, and I thought, "Good, the color exists in the external world." But in the second half I got restless, and when I saw the snuffboxes again, they were no longer indigo -- they were blue, mauve, pink. I've never seen that color since.
It took a mountain of amphetamine, mescaline, and cannabis to launch me into that space. But Monteverdi did it too.
See also: Oliver Sacks on music and amnesia
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.