In 2004, Matt Sax had a meltdown of sorts.

“I wondered ‘What am I doing with my life?’ ” he recalls.

He was 20.

The Mamaroneck native – then a sophomore theater major at Northwestern – decided to do something “absolutely extreme,” entering a play in the Edinburgh International Fringe Festival.

The extreme part was that he hadn’t written a word of the script.

“I knew I wanted to write a hip-hop-themed piece, but I didn’t know what it wanted to be,” he says. “I knew I wanted to play all the parts. I knew I wanted to write it and to write all the music and put the whole thing on my shoulders.”

The Fringe said yes.

Sax raised $20,000 to get to Scotland, ”$15,000 of it from Northwestern, all on the premise that I had this amazing show that I had written, and I still hadn’t written one word.”

Then he started writing.

He wrote “Clay,” about Clifford, a suburban kid from a broken home who travels to Brooklyn and discovers the world of hip-hop. He comes to the attention of Sir John, who becomes a mentor and friend, and before too long, Clifford has been molded into Clay, a hip-hop star on the rise.

Sax glides effortlessly among seven distinct characters in “Clay,” shifting from a young Clifford to his father to his mother in the blink of an eye or by scrunching up his face.

“Clay” became a bona fide hit at Edinburgh, and went on to successful productions at Chicago’s Lookingglass Theater and the Mark Taper Forum in Los Angeles. It’s currently playing at Kansas City Rep, where Sax’s director, Eric Rosen, is a new artistic director.

But it may be that what’s about to happen to “Clay” is the most exciting part of the story: Sax’s one-man, hip-hop musical has been tapped to kick off LCT3, Lincoln Center Theater’s ambitious effort to develop new artists and younger audiences.

From Oct. 4 through Nov. 8, “Clay” will get a full production at The Duke on 42nd Street, putting it on New York’s theatrical map.

Before Paige Evans became the head of LCT3, she worked at Manhattan Theater Club with Sax’s friend from Mamaroneck High School, Jocey Florence.

It was Florence who brought Evans to see a workshop presentation of “Clay” last year.

Evans saw promise.

“I thought he was very talented as an actor and writer, that the piece was complicated but accessible in its writing and that he performed the different roles really well,” she says. “Also, it was dynamic and I felt it would be an event and an exciting thing to start with.”

LCT3 is the brainchild of André Bishop, artistic director of Lincoln Center Theater, who has been wanting to bring in a new generation of artists and audiences, Evans says. Once LCT3 brings emerging writers, directors and designers in, Bishop hopes they’ll make Lincoln Center their artistic home.

The Duke on 42nd Street is far from Lincoln Center, but future LCT3 productions will have a brand-new artistic home. A capital campaign will build a theater on the roof of the Vivian Beaumont Theater, expanding the performing-arts theater complex.

The story of “Clay” has not changed greatly from the version audiences saw in a cavelike performance space in Edinburgh four years ago. Director Rosen has shaped the play, convincing Sax to do more with less.

As it is, Sax’s only prop is a microphone and his prodigious skill at beatboxing, with which he creates a world in which a boy loses his family, loses his way and finds a lifeline in hip-hop. The story is a compelling jumble of images, some of them jarring, some funny, some disturbing.

During the L.A. run, Sax won permission to open “Clay” up to high school groups.

“By the end of the run, to see 90-year-old Jewish women sitting next to 16-year-old black girls was an amazing thing,” he says. “That’s been the idea of this show: to get younger audiences into the theater.”

While Sax admits to feeling pressure of being the first LCT3 act out of the box, “it is exactly what I want to be doing.”

“I don’t have to get a waitering job just yet, although we’ll see how things go,” he says with a laugh.

The fact that all LCT3 tickets will be $20 is a huge draw, Sax says.

“Kids don’t want to pay 90 bucks to see a show, and they shouldn’t have to,” he adds. “Theater should not be looked at as this high-culture thing that only certain people can go to.”

Like Lincoln Center.

“That’s what’s so amazing about them doing this – that they’re willing to support the idea of getting new faces into the theater. The theater can hold these stories.”

The self-described “nerdy Jewish kid from Westchester” concedes that his is not the first face one might associate with a hip-hop musical, but he sees the form as adaptable to all comers.

“Hip-hop is flexible to hold all kinds of stories,” he says. “To hold the story of someone who has lived on the streets, to hold rock music and country music. It is a form that can hold all those. And there’s an amazing theatricality to it.”

The first rap album he owned, Notorious B.I.G.’s 1994 disc, “Ready to Die,” concludes with the track “Suicidal Thoughts,” in which Biggie calls up producer Sean “P. Diddy” Combs, talks about suicide and then kills himself while he’s on the phone.

That dramatic moment plays out, in a different setting, in “Clay.”

To write a hip-hop show, Sax had to teach himself how to write hip-hop.

“Most of the lyrics I wrote were in the first incarnation of the show,” he says. “I had never rapped before I wrote the show.”

He also wrote the music, which plays continuously throughout the action, as Sax raps and talks over it.

“To say that hip-hop hasn’t been around would be a lie,” Sax says. “It is now in its third full generation of life. Theater tends to be at least 10 years behind the curve in terms of what’s happening culturally.

“I’m not breaking new ground with hip-hop, but being able to marry it with theater is an exciting thing and something that you’re seeing more and more. Look at ‘In the Heights.’ ”

Sax was also influenced by more conventional theater.

Sir John the mentor is a nod to Falstaff in Shakespeare’s “Henry IV,” which Sax saw in a marathon production in London when he was 16.

A hip-hop musical is broad enough, Sax says, to grab snippets from a rap pioneer like Biggie and a theater great like Shakespeare.

And Lincoln Center is big enough to let that voice be heard.

“I’m rapping and Lincoln Center Theater is producing it,” he says shaking his head.

“Amazing.”

“CLAY”
Where: An LCT3 production at The Duke on 42nd Street, 229 W. 42nd St.
When: Oct. 6 through Nov. 8.
Tickets: $20.
Call: 646-223-3010.
Web: www.lct.org.

Photo by Tania Savayan: Matt Sax brings his one-man hip-hop musical, “Clay,” to New York to launch Lincoln Center’s ambitious push to attract new audiences.