Even on his earliest albums, Prince seemed to be speaking a new musical language — one that sounded poised to sweep aside the old guard in the rhythm & blues tradition from which he burst forth. Yet even as he prepared to help usher in a new era, he remained actively indebted to — and willing to collaborate with — his forbears.

One late-period example that particularly stands out is "So What the Fuss," the 2005 single that launched the protracted promotional campaign for Stevie Wonder's 25th studio LP, A Time to Love. The song, which arrived in late March (more than six months before the album's release), featured Prince playing guitar — a superstar summit that reflected the deep, genuine appreciation the artists had long shared.

"I use Stevie Wonder as an inspiration, whom I look up to a great deal just for the way that he crafted music and his connection to the spirit," Prince told Larry King in 1999. "And boy, back then I used him as a role model in trying to play all the instruments and be very self-contained and keep my vision clear."

A young Prince using Stevie Wonder as a role model made perfect sense, but it was easy to imagine Wonder — already an elder statesman when Prince made his breakthrough — being put off by the newcomer's brash attitude and heavy sexual overtones, at least if you were only familiar with the adult contemporary sound Wonder had drifted into by the mid-'80s. Yet despite their differing styles, the admiration society was decidedly mutual.

Watch Stevie Wonder's "So What The Fuss" Video

"He could play classical music if he wanted to. He could play jazz if he wanted to, he could play country if he wanted to. He played rock, you know, he played blues. He played pop. He played everything," Wonder told Anderson Cooper after Prince's passing. "And [he was] very cognizant of what his responsibility was as a musician and a human being."

Wonder's love for Prince was made fully manifest in the following weeks. He closed a Los Angeles tribute show by leading the performers through "Purple Rain" — and played the song again at the Billboard Music Awards. Long after Prince was laid to rest, his absence seemed to weigh heavy on Wonder.

"It's a heartbreak and I was shocked," he later explained. "You know, in this journey of music, we as artists that create the reflection of society and reflect, really, the people that really want to see a better world, a better people, a unity of people, all those things – as did his music do and will continue to do for those of us who will continue to listen to it – it's a heartbreak to lose a member of that army of love."

In fact, much like many of Prince's fans, Wonder has taken a sobering lesson of mortality from the sudden end to his musical disciple and onetime collaborator's tragically shortened career. "We had previously, very recently talked," he told NPR a year later. "Talked about his future and things that he wanted to do and how inspired he was with the things he wanted to do. It lets you know: Hey, tomorrow's not promised to anyone."