It’s hard to imagine an artist more committed to a singular vision than Prince Rogers Nelson. His career began in 1978, with the release of his debut album, For You, and ended nearly 40 albums later, in 2016, when he was found unresponsive after an accidental drug overdose at Paisley Park, his recording compound near Minneapolis. Prince scrambled and recalibrated pop music to suit his own wild and beautiful tastes. His playful songwriting, his lavish wardrobe (platform boots, ruffled cravats, bespoke suits in glorious fabrics), the ferocious yet elegant way he handled a guitar—everything about Prince’s lifestyle and persona felt, and continues to feel, unprecedented and unsurpassed.

The precise mechanics of Prince’s talent—how he was able to conjure such gleeful and transporting melodies—has always been something of a mystery, even to his most devoted fans. When he died, he was at work on a memoir, The Beautiful Ones, the first 50-odd handwritten pages of which Random House will publish in October in an edition including rare photographs, scrapbooks and lyric sheets. Had he lived to complete it, one wonders whether the book would have clarified more about what drove him. But then, Prince didn’t want to be understood. He once told Details magazine that his fans needn’t look into his inner self at all: “There’s not much I want them to know about me, other than the music.”

He was born in Minneapolis in 1958. His mother was a jazz singer, his father a pianist and songwriter. He was a musical polymath from an early age. He signed with Warner Bros. in 1977, when he was just 19, and he arranged, composed and played almost all of the 27 instruments on his debut album himself. In 1984, Prince starred in Purple Rain, a semi-autobiographical film designed to showcase his extraordinary charisma. Onstage, he appeared so otherworldly and elegant that it was impossible to look away.

Purple Rain climaxes with a seven-minute performance of the title song at First Avenue, a beloved music club in downtown Minneapolis. Prince reportedly wrote “Purple Rain” (the song) to perform as a country-tinged duet with Stevie Nicks, but she was so overwhelmed by the intensity of the composition that she couldn’t bring herself to generate any lyrics for it. Prince responded by making the song even heavier and more epic, building toward a closing guitar solo so dizzying and gorgeous it’s hard not to feel like a slightly different person after you hear it.

The guitar Prince plays in this climactic scene was custom-made for him by a luthier at a Minneapolis music shop called Knut-Koupee Enterprises. Prince’s famous “symbol”—a combination of the Roman symbols for Mars and Venus, corresponding to male and female—is inlaid in a repeating pattern on the fret board, and the upper half of the body curls into a cloudlike wisp. It made sense, even then, that Prince would require an instrument that didn’t resemble anything anyone else was playing. Knut-Koupee made three so-called “cloud” guitars for Prince in the early 1980s. While on tour, Prince would often thrash one onstage, then ship it back to Minneapolis for repairs.

In 1993, Prince gave a cloud guitar to the Smithsonian Institution, but he didn’t include any information about the instrument’s origins. But earlier this year, John Woodland, the conservator for Prince’s guitar collection, who has been researching the history of the cloud guitars, reached out to the Smithsonian with a sneaking suspicion. After the guitar underwent a CT scan and extensive paint analysis, what they found was a shocker: “All evidence suggests that this was the first cloud guitar ever built for Prince,” John Troutman, curator of American music at the National Museum of American History, told me—meaning it was also the same guitar Prince plays in Purple Rain, as well as in the 1985 music video for the single “Raspberry Beret.” It was then repainted to appear on the cover of the 1987 album Sign o’ the Times. This wasn’t just a cloud guitar, in other words, it was the cloud guitar—the instrument responsible for some of the most iconic sounds and images in American popular music. “The guitar is an extraordinary gift from Prince to the American people,” Troutman says.

More than three years after his death, it’s tempting to stare at the cloud guitar and wish for more clues, more time, more music. What was Prince thinking when he held it in his hands? What strange, metaphysical currencies might he have been channeling? Of course, we’ll never know, which is surely how Prince would have preferred it. The mystery of his life and work is an essential part of his magic—it always was. Which makes it all the more thrilling to look, to listen and to wonder.