At the time, Bob Dylan was living in a tent in the studio gardens, and every now and then he would show up for a drink, then disappear again. I asked him if he wanted to contribute to the album by writing, singing, playing, or doing something else. One day he came to offer me a song, "Sign Language," which he had played for me in New York. He told me he had written it all in one go, not quite knowing what it was about.

.: From the Autobiography of Eric Clapton (which I'm slowly continuing to read here in Morocco between a couscous and a pasta...)

Bob Dylan & Eric Clapton - Sign Language