If you were going to list the reasons for the mostly unexpected crossover success of Macklemore & Ryan Lewis' "Thrift Shop," there'd be a number of factors to point to: Macklemore's hard-earned fanbase and rep as an independent touring rapper, the song's funky, skronked-out beat and sax hook (courtesy of Lewis), the song's quickly viral music video parodying traditional hip-hop excess. But perhaps at the top of the list would be the song's sturdy, soulful, and instantly memorable hook: "I'm gonna pop some tags, only got twenty dollars in my pocket / I-I-I'm hunting, looking for a come-up / This is fu-cking awe-soommme..."

That hook is the work of the Seattle-based singer Michael Wansley, known better as "Wanz," a 51-year-old music vet who had never cracked the Hot 100 before, let alone reached its top spot. In fact, there were a whole lot of things that Wanz had never done before getting the call to be on "Thrift Shop"—never been on a music video shoot, never been out on tour, certainly never been on Ellen.

In fact, up until a couple weeks ago, Wansley had a full-time job as a Software Test Engineer, testing out new applications. "I kind of gave up a long time ago on making money making music," Wanz explains. "[The job] turned out to be the godsend of my life because I'd been living kinda hand-to-mouth, but I was finally making a gainful salary, had benefits...So I thought that was going to be my life, and music was pretty much going to be a hobby. "

That "hobby" had been one that Wanz had indulged in for the great majority of his life, having grown up a voracious pop listener ("I read Billboard like most people read People," he says of his youth), and having dreamed of being a singer ever since he was a kid, being tested on the schoolyard by his classmates on his pop chops. "My first memory is when I'm five years old...a bunch of kids had been quizzing me on songs," he recalls. "Each one that they quiz me on, I sing it. 'Bet you don't know this one!' and I'd sing it. 'Bet you don't know this one!' and I'd sing it." From there, he would be compared by family and classmates to young Michael Jackson—who, believe it or not, was roughly Wansley's peer, age-wise.

Wansley's life was spent immersed in music, through his days studying jazz at Central Washington University in Ellensburg. Having taught himself to play bass, He spent time in a number of different rock bands at this time, most notably the group Boys Will Be Boys, whose regular gigs would eventually inspire him to leave behind his education and move to Seattle, where he has stuck around for over a quarter-century. In Seattle in the late-'80s, he recalls being around "for when the grunge thing happened," having patronized the same bars as a number of musicians in the bands who ended up striking it big, even once chilling at the house of Pearl Jam guitarist Stone Gossard.

However, Wanz never hit it big in the same way as any of those bands, and as he settled down—with the full-time job, and with two kids, the now 26-year-old Terrence and 19-year-old Aaren, who he still lives with—gradually his role as a musician came to be as a hired gun, singing hooks for other artists. "At the time it was $25 an hour for me to come and sing the hook for you, $40 an hour if I had to write it," he says of his going rate at the time. His biggest thrill as a musician in recent years was landing a role in the chorus of the Seattle Opera's production of Porgy and Bess. "I thought that was my high-water mark," Wanz says.

Wansley was sitting in bed on a Monday night, "watching Nightline, surfing Facebook," when he was first approached to sing on "Thrift Shop," by a producer mutual friend of he and Ryan Lewis'. "He says, 'Yeah, Ryan called, he's looking for a guy who sounds like Nate Dogg,'" says Wanz, referring to the legendary G-Funk hook man. "And we both laughed, because I'd been recording hooks with my friend for a while, and that was kind of my rep. I was Nate Dogg of the North End of Seattle." Wanz accepted the gig, though he was only familiar with Macklemore by reputation, having never heard of any of his music.

Despite being warned by the mutual friend that it might be a while before Macklemore and Lewis followed up with him about the song, Wanz says they called him just five minutes later, and later that night, he was at Ryan's studio, ready to record. "Ben [Haggerty, Macklemore's real name] says, 'What we're doing, we're doing this song, It's about thrift shopping,' and he shows me the line, and just kinda hums it, and says the words in rhythm, and I say 'OK, so it's something like this,' and I sang what you hear now," Wansley remembers. "Go in the booth, get levels, and less than 45 minutes later, we were done."

Though Lewis told him he "totally killed it" with his vocal, Wanz left the studio not expecting to hear about the song again. "'Coz that's kinda the way it's always been," he explains. "I go in and record a hook for a guy, and then I never hear from him again." He was surprised when a few weeks later, he got a call at his work from Lewis asking if he could make the song's video shoot. "I said 'I think so,' and got the day off, went and got the [creamsicle suit from the video], and shot it." The shoot was a surreal, but enjoyable experience for Wanz. "I had a great time," he says. "I couldn't believe it, I'm like four feet from the camera, and the focus is on me, and this is all stuff that had never happened for me before."

When the video came out, it was the first time Wansley actually heard the finished song, including his vocal. "I had never sounded that big, and that full, on a track where the bass was so deep," he remembers. "It was over-the-top good. But I still really had no idea how it would…I didn't know much about their fanbase." With the video's near-instant success, he would quickly learn. "We're at the video release party, and [Macklemore] goes, 'Well, do you have a Twitter account?'" Wanz did not. "He had a smile on his face, and he just went deadpan, and just goes 'Man, you need to get a Twitter account.'" (Started just a few months ago, @teewanz already has over 3,000 followers.)

Shortly thereafter, Wansley was out on tour with Macklemore's crew, doing a series of West Coast dates that had him playing in front of audiences bigger than he'd ever seen in his life. ("Talk about drinking from a firehouse, it's like, 'Wow, my second gig is in front of 7500 people,'" he recalls.) But soon, this would bring Wanz to a crossroads in his life, as he burned through his vacation days at work and had to make a decision about whether he wanted to keep his job, or stay out on the road.

A gig at the legendary Fillmore West club made the choice a simple one. "I stood in that hall, and looked around, and just broke down into tears," Wansley recalls. "To be standing in that room that is like a mecca for musicians, all the people that had played there were all the people that I had grew up listening to and singing...that's a moment that I'll never forget." The next day, he got a call from his office's HR department, and he told them his decision. "I said 'I just did a dream gig at a place that I've always worshipped, and I have to keep continuing on this dream, because at my age, I don't know when this kind of opportunity is ever gonna happen again.' And I walked away from the job."

Next, Wanz is preparing to tour Australia with Macklemore, and he's also working on his own brand, setting up a merch website, working on a new EP, and looking to find a way to profit off a series of sayings he's coined over the years, referred to collectively by at least one tourmate as "The Book of Wanz." He's also taken to personally greeting fans on line outside his shows, "preaching to them as well, passing on this stuff," though he refuses to indulge requests for a personalized "This is fu-cking awe-some." ("They're like 'Can you do that? Can you do that? And I'm like 'I could, but I'm not going to,'" he relates, laughing.)

Asked if he's worried about being pigeonholed by that one lyric, Wanz says he's already made peace with it. "My dad always used to say, 'Make sure you dance with the date that brung ya,'" he explains. "I'm always gonna be the 'Thrift Shop' guy. Everybody has their thing, and that's gonna be mine. The question for me has been, 'Am I gonna stay that guy, or am I gonna be the guy who came in as this, and then they found everything else?'"

In the meantime, Wanz is enjoying his long-delayed success, getting to make his kids proud. "The younger one just sits and plays online games and people on Tumblr don't believe he's my kid," he says of his son Aaren. "They're like, Skyping with him and I come into the frame, and they're like 'Oh my God!!!'" And recently, Wansley was given a shoutout by one of his chorus co-stars in Porgy and Bess, which sort of sums up his life story to this point:

"Who would've known the blind man from Catfish Corner would blow up to sing the hook on the number-one song on the country? Good on ya!""