As McCoy prepared to leave, Dylan surprised him again. “Listen, I’m getting ready to do this song,” he told the Nashville session ace. “Why don’t you sit in?”

“What do you want me to play?” McCoy—who didn’t have any of his instruments with him—asked.

“There’s an acoustic guitar over there,” Dylan said. “Just grab that.”

Less than an hour later, they had a master take of “Desolation Row” in the can, an eleven-minute acoustic version that would close out Highway 61 Revisited. McCoy improvised the flamenco-inspired guitar fills that became the track’s musical highlight, saying later he tried to imagine what Grady Martin, the legendary Nashville session guitarist, would have played on the song.

After McCoy left the studio, Johnston told Dylan, “Now see how easy that was. That’s how it would be in Nashville.” Dylan put his hand to his chin thoughtfully and said, “Hmmm.”
— from That Thin Wild Mercury Sound by Daryl Sanders