He's a short, husky white guy with long, curly hair that's thinning on top, and he bears a striking resemblance to former porn actor Ron Jeremy. Only when he opens his mouth, projecting a silky tenor, that it all starts to make sense.
Tillmann, 33, grew up a fan of wide array of the msuic emanating from his native Minnesota: everything from Prince, to alternative rock bands like Husker Du and The Replacements.
"I've always loved R&B, but at the same time I was listening to the Dead Kennedys and other punk," Tillmann said during a recent phone interview. "I kept my feet in both worlds. But I've always listened to a range of music."
He followed a traditional path initially. Tillmann played bass and sang in a punk trio called Calvin Krime that toured the country. After splitting in 1998, he started performing soft rock under the stage name Sean Na Na.
"I always knew I could sing," Tillmann said, but the new vehicle wasn't fulfilling his creative needs. By then he was burnt out on guitar rock, but his concerts weren't wild and sexual enough for his liking.
"Showmanship has always been important to me," Tillmann said.
As Sean Na Na, he began closing concerts with a rendition of R. Kelly's "When a Woman's Fed Up." Soon he was writing and singing more in that vein. In 2001 he released his self-titled debut as Har Mar Superstar, the name derived from a shopping center in Minnesota called the Har Mar Mall.
At first, Tillmann performed as Har Mar alone, using prerecorded tracks. Feeling he had to overcompensate, Tillmann became notorious for stripping to his skivvies and exhibiting sexually-charged behavior. His dance moves, flaunted in memorable music videos for songs including "DUI" and "Power Lunch," come not from lessons but "a lot of mirror dancing to Michael Jackson records as a 6-year-old."
He admits to having confidence in his own skin, but not necessarily on the level of Har Mar Superstar.
"If there's a vehicle in which to bring it out and be able to flaunt it (then that helps)," Tillmann said. "But I don't think anyone's ever fully confident until they're in their 30s. This helped me speed up that process."
Performing Har Mar's lascivious music used to make Tillmann feel like he was his alter ego.
"Now I've sort of become that person," he said. "It's fun. You can definitely channel stuff. I can go a little further with things I say and do. At the same time, it's all part of the same package at this point."
Now Har Mar has his own band and backing female vocalists.
"It's more like a revue now; funny and party-like, just encouraging people to take off their clothes and make out and get sweaty," Tillmann said.
The ladies evidently love it. That brings the guys out. It's not uncommon for Har Mar to get multiple hi-fives and thank-yous from dudes.
"I'm liberating chubby men everywhere," Tillmann said with a laugh.
Given his background, he's reaching many walks of life too.
"There's punk kids and pop fans," Tillmann said of his audience. "It's really fun to have a diverse crowd like that."
Har Mar may have been more flamboyant than consummate starting off, but after four albums, including 2009's Dark Touches, he's found his groove.
"The songs have come around to the point where they could be played next to any pop or R&B song," Tillmann said. "I think it's my voice that keeps it from being total camp. I've gotten really good at singing. My voice has never sounded better than it does now. The fact I can flaunt that makes everything more real."
He's still an outlier in the rhythm-and-blues community though.
"It's not like I'm reaching out to Boyz II Men to cameo on my album," Tillmann said. "I'd love to do an R&B tour, but I also like to hang out in rock clubs. That's where my friends are. It feels more like home to me."
He's got too many other offbeat projects in the works to worry about where he fits in. Besides a new Har Mar record, which Tillmann says sounds like the glory days of Stax Records, he's playing guitar in a "David Lynch-y" band called Fur Pillows and touring with another collective named Gayngs that plays soft rock in the style of 10cc. The latter, which also includes Bon Iver's Justin Vernon, is recording an album that Tillmann promises sounds like early-'90s New Edition.
"Instead of just hanging out and going to bars, which I do a lot anyway, I like to be productive," he said. "If I didn't I'd go crazy."
Har Mar Superstar is still Tillmann's main pursuit though. To some it may always be parody, while others find it manumitting. Tillmann doesn't care either way.
"If people are having a good time but they think it's a joke, that's totally cool," he said. "But if people are seriously into the music, I appreciate that too. I just want everyone to come and have a good time however they want to perceive it. It's not my place to tell them what to think of me."