It's that age-old story: Melissa Li and Kit Yan bumped into each other. Then they formed a rock band. Then they became friends. Then they were a hit. Then they started to hate each other. Then they became pals again. Then they wrote a musical about all of it.

Li and Yan's "Interstate" has its world premiere tonight at Mixed Blood Theatre, climaxing a story they've been telling since they met in Boston a dozen years ago.

"It was at this queer, spoken-word cabaret and I said, 'Hey, let's quit our jobs and go on tour,' " said Yan, 35, who splits time between New York and Minneapolis, where they're a Many Voices fellow at the Playwrights' Center. (Yan, who is transgender, prefers "they/them" pronouns.)

"And then we did," said Li, 36, who lives in Baltimore and New York. "We played festivals, coffeehouses, house parties — some paid, some unpaid. It was supposed to be a three-month tour, but it was so successful and life-changing that we ended up doing it for two years."

By that point, their band, Good Asian Drivers, had recorded a CD, toured to 32 states (they played the now-defunct Pi Bar in Minneapolis) and grown good and sick of each other. But that's getting ahead of the story.

While "Interstate" is not strictly autobiographical, it does blend details of their lives with the folk/rock tradition of Li's music (represented by a character named Adrian) and the spoken-word poetry of Yan (in the form of a character named Dash). "Interstate" adds in their parents and a trans teenager named Henry who sparks to their music and to Dash's journey, which parallels his own.

When the tour ended and the hatred began, the Good Asian Drivers went their separate ways. Yan wrote poetry, trying to make sense of the parting. Li sent the occasional text to Yan ("She's way more mature than me") so, when Yan eventually moved to Brooklyn, not far from Li, it seemed like a good time to share the poems.

"I showed them to Melissa. We sat in Prospect Park, under a tree, and I said, 'What do you think about these poems?' " Yan recalled.

Umm ...

"I said they sucked," Li said. "They were not good. Just ramblings."

"Absolutely," agreed Yan. "I was essentially showing Melissa my 50-page journal entry."

Yan had never written a musical, had not even seen that many, but thought there might be one in the Good Asian Drivers story. Meanwhile, Li had actual experience in the form: She won a prestigious Jonathan Larson Grant, named for the composer of "Rent." (Li's 2007 co-recipients included Benj Pasek and Justin Paul, eventual songwriters of "Dear Evan Hansen" and "La La Land.")

"I said, 'I think this is the beginning of a musical,' " Yan said.

"I probably said, 'I don't like musicals, I'll tell you that right now.' I definitely, definitely did not want to write a musical," Li said. "The reason I ended up saying yes is that within the two years we were apart, I had been thinking about our experience on the road and about doing something about it."

"Interstate" boasts at least three styles of songs. There are Adrian's folk-rock tunes, which lean more toward rock at Mixed Blood because Li only had her guitar but Mixed Blood will have a four-piece band. There are Dash's spoken-word pieces that blend with or are underscored by music. And there are Henry's pop songs, influenced by the electronic dance music that a teenager might listen to (although his sunny "I Don't Look" has a '60s vibe).

Jeremy B. Cohen, producing artistic director of Playwrights' Center, first heard Li/Yan songs during a workshop of another of their musicals, "Miss Step." He sparked to their optimism.

"It is rare I've been at the Playwrights' Center and seen an audience scream and cheer and rise to their feet in such delight," Cohen said. "They do this beautiful job of articulating the challenges in the world and then having their characters pull themselves up as they confront them."

Li sees music as an accessible entry point into the show.

"I'm into writing music people can connect to," the composer said. "I think people can feel more things when they are listening to music they understand. It opens their hearts to the story."

Many of the songs and poems have an activist bent. Commerce co-opts queerness in "Not My Gay Pride," and "Kiss This Bar Goodbye" features a trans man's goodbye to his mom.

Like most musicals, "Interstate" has evolved significantly. A love triangle between Adrian, Dash and their drummer disappeared while Henry's prominence has grown throughout two dozen drafts of the show, in part because audiences at New York workshop productions responded so enthusiastically to him.

Over the years, time enabled the creators to gain perspective on the piece.

"We felt the pressure of having to be perfect at first," said Li, who, like Adrian, is a lesbian.

"Finally, we let that go and said, 'We're just going to tell these stories about people who are queer, trans and Asian, who are activists and artists and we're going to talk about their relationships and about them as individuals, rather than them having to represent their identities,' " Yan said. "A major theme we explore is toxic masculinity, even from a trans person's perspective. Dash is a trans man but he's making a lot of mistakes. He's being sexist. He doesn't know yet how to be a man."

The workshops convinced Li and Yan they were on track.

"At New York Theater Festival, we got a crowd of people every night who don't always show up to Broadway. A lot of young folks, people of color, queer and trans people. It was a loud audience, more like a poetry slam, where people will cheer and whoop," Yan said. "We thought, 'This is the room we want to be in.' "

The collaborators hope for more whooping in Minneapolis. But, whoops or not, their friendship won't depend on how "Interstate" is received. (For one thing, they're also at work on several other musicals.)

"No," said Yan, when asked if things still feel shaky. "But when we hated each other, it was the worst breakup of my life."

Li agreed: "I can't imagine us not being friends now. Honestly, when you get older, you feel like, 'I don't have the energy for that.' "

Not that either of them saw any of this coming when they met up in the park seven years ago.

"If you had told me in 2013 that we were still going to be working on this show now, I would not have started it. I wouldn't have believed you. I'd be, 'Why would I work on this thing for seven years?' " Li asked.

"The joke's on 2013 Melissa," Yan replied. "Now, it's our full-time job!"

Chris Hewitt • 612-673-4367