In the spring of 2009, four performances of an original work were staged by a group of friends in the Basement Arts theater at the University of Michigan. Those actors, writers, and musicians had a hit on their hands and went on to form StarKid, staging four more Internet-only original musical parodies.
Three years later, that show, “A Very Potter Musical,” recorded at Basement Arts, has played on YouTube nearly 9 million times.
And in total, Starkid’s work — traditional musical theater performed in front of a live audience only often enough to capture it on video in a three-camera sitcom setting — has been seen online a staggering 125 million times. Its cast recording charted on Billboard.
Three years later, Darren Criss, who played Harry Potter in “AVPM” and its sequel long before he got the role of Blaine on “Glee,” is sitting in his car in the driveway outside his Los Angeles home. He is trying to explain how a theater troupe without its own theater is on a 21-city concert tour — including a stop Saturday at Boston’s House of Blues — even though the performers are actors by trade and not singers.
“I don’t envy your job trying to sum up what StarKid is,” Criss said. “We’ve had enough trouble trying to do that ourselves — and we’re in it.
“There is no model like us. We’re not an amazing new thing, as much as we are an accidental surprise for ourselves. We never planned on any of this. It’s all very accidental and quite organic.’’
Joe Walker has a similar take. Walker played Lord Voldemort in “AVPM” and Batman in the most recent show, “Holy Musical B@man!” He’s on one of the two StarKid tour buses headed across the country.
Walker grew up in Cambridge, attending the Atrium School in Watertown, Fessenden in Newton, and Buckingham, Browne, & Nichols in Cambridge, before enrolling in Michigan’s theater program.
Working with almost all Midwesterners, he is excited about the upcoming Boston stop. “It’s always nice to have people come to where I’m from,’’ he said, “because you can sort of point around and say, ‘This is maybe kind of why I am the way I am.’ I say, ‘Look, everyone drives like this here.’ ”
Three years ago, Walker and Criss and others were in their senior year and “Potter” was their final show. Each and every StarKid member says being in it, working on it with friends they had worked with for years, was the most fun they ever had. They decided to videotape the show as a souvenir.
The Potter show was put together, Criss remembers, “in maybe three weeks, and I wrote most of the songs the week of.”
Matt Lang, “Potter” director, didn’t want to burn 30 DVDs, says Walker, so he put it on YouTube. “And then suddenly, bam, 200,000 views in a day, and you go, ‘Oh wow, people like this.’ ”
There had been shows before “Potter.” Lang, his brother Nick, Brian Holden, and Criss had staged “The Hobbit,” “The Lord of the Rings,” and “Jurassic Park,” said Criss. But those shows were never taped.
“People always say, ‘Darren, good move with the first musical being a Potter video and targeting an already large fan base on a new medium like YouTube. Smart move,’ ” Criss says. “And I’m like, ‘I’m not that smart!’ Never in a million years would I have strategized that bizarre plan.’’
Criss had moved to Los Angeles after graduation, as had Holden and the Lang brothers. As the Potter video became huge, the friends looked around, deciding what to do next.
They decided to form StarKid. Since the players — now graduated — were spread over the country, Chicago was chosen as the company’s home base mostly because of its central location. Troupe members Lauren Lopez and Julia Albain, for example, had moved to New York. But they kept coming back for StarKid projects, such as “The Very Potter Sequel,” and by the fall of 2010 they were moving to Chicago.
“After the sequel there was this buzz that kind of started that maybe we should get in one space and kind of do this for real,’’ said Albain. “That was when we said, ‘OK, let’s try to do this more frequently, and let’s see what we can build out of this.’’
With five full-length musicals now to its name, StarKid hit the road. In the fall, it was the Space Tour. This time, it’s the Apocalyptour.
“We don’t experience the width and depth of our audience, because it is all online,’’ Albain says. “It’s kind of amazing to just see however many tens of thousands — when it’s all said and done — young people getting excited about theater, it doesn’t just happen.’’
Lopez, who played Draco Malfoy in “AVPM,” is one of the nine performers on the current tour. Albain, meanwhile, is serving as director.
“In a lot of ways, it’s a very musical theater production, but it’s not a musical per se,’’ she said, trying to explain what the live event will be like. “There is a story, but there’s not a full script. It’s basically a revue of songs from all of our different shows, but, because we are a theater group, we try to add a theatrical homage and a loose story, just because that’s what we do. So, it’s an odd duck.’’
Among the future plans is the long-rumored “Harry Potter 3,” or “The Threequel,” a project whose mention excites everyone living in the StarKid world.
The tour ends June 10 with a sold-out show at Roseland Ballroom in New York. Criss, whose other projects have kept him from taking part in the bulk of the tour, will make an appearance, as he did at one of the LA dates.
For Criss, there’s nothing like it — and that’s from someone who has been out on the “Glee” tour. These are his friends. There is no place any of them would rather be.
“Most of the people in that [concert hall] didn’t casually come across [StarKid],” said Criss. “It is such a niche audience. Everyone there is excited to be there – including the people on stage.”
For information about StarKid, go to www.starkid
.com. John Vitti can be reached at jvitti@globe