Kurt Cobain’s guitar playing influenced a generation. (AP/AP)

Kurt Cobain, voice of a generation.

Also, that generation’s guitar teacher.

It’s been 20 years this month since the Nirvana frontman abandoned this plane, leaving behind a trove of power chords that can still be heard beneath the tender fingertips of anyone learning to play the electric guitar.

Among the multitudes who reportedly got their start strumming Nirvana riffs: Rostam Batmanglij of Vampire Weekend, rising Australian songwriter Courtney Barnett, who says she picked up “Come As You Are” at age 10, and countless other kids the world over.

“Nirvana gave a whole new generation of musicians a place to begin, a place to get a foothold,” says Brad Tolinski, editor in chief of Guitar World, the magazine that — with Cobain’s blessing — first began publishing notation to Nirvana songs in 1992. “He was a fantastic musician,” Tolinski says, “and I think he liked the idea of people playing his music.”

For ’90s babies who didn’t have the dough or the discipline for guitar lessons, those magazines did what so many YouTube tutorials are still doing today, and somewhere, Cobain has to be smiling. As an adolescent, he reportedly took just a month of guitar lessons — enough to learn the riff to AC/DC’s “Back in Black” and figure out “Louie Louie” and “My Best Friend’s Girl” later on.

We all know the rest. He quickly set out to write his own songs, formed Nirvana with bassist Krist Novoselic in 1987, completely hijacked the course of rock and roll in 1991, became famous beyond anyone’s wildest imagination and ended his life in April 1994.

Before Nirvana, punk pioneers the Ramones were known as the band whose songbook could be decoded with the least amount of expertise. But when Nirvana’s second album, “Nevermind,” exploded in 1991, that changed. By moving an in­cred­ibly simple power chord shape up and down the fret board, newbies could learn to play some of the most popular rock riffs on the planet in the course of an afternoon.

“I started playing guitar around the time that ‘Nevermind’ came out,” says Jack Antonoff, guitarist of platinum-selling rock band fun. and new project Bleachers. “Being able to mimic something you idolize like that was really encouraging — which is probably why kids aren’t into super-prog jazz. They can’t do it.”

Cobain obviously wasn’t a fan of florid guitar derring-do, either. His rudimentary style can perhaps be heard most clearly on the band’s “MTV Unplugged in New York” album when he flubs the guitar solo to David Bowie’s “The Man Who Sold the World” with a shoulder shrug. The guitar gods were fallible after all.

“He couldn’t play — and had no interest in trying to learn — Eddie Van Halen speed scales or in­cred­ibly complicated jazz chords,” says Butch Vig, the legendary producer behind “Nevermind.” “But he was a great player with an instinct for writing really great, hooky, rhythmic, riffy chord patterns.”

Part of Vig’s task during the recording of “Nevermind” was making Cobain’s scrappy riffs sound as massive on tape as they did when the band was dumping out decibels on stage. He often had to coax Cobain into double-tracking his guitar parts, explaining that the Pixies — a band Cobain worshiped — had done it.

But Vig says that even at its most raw, Cobain’s guitar playing was always highly articulate and deeply expressive. “He had a kind of primal instinct for playing the guitar,” Vig says. “And a lot of that comes from [his] punk background. . . . You were forced to become your own teacher.”

Cobain’s songs preached do-it-yourself-ism almost subliminally. Eleanor Friedberger says she never had a proper guitar teacher, but she did have an older brother — her future Fiery Furnaces bandmate, Matthew Friedberger — who gave her an electric guitar when she was a freshman in college.

Along with it: a notebook filled with scribbled instructions on how to play Nirvana’s “Smells Like Teen Spirit” and “Sweet Jane” by the Velvet Underground.

“It’s cool those were the two songs I got to learn first — it’s what I loved the most at the time,” she says. “I’m still not a great guitar player, but being able to follow along with those chords, it’s like, ‘Anybody can do this. This isn’t hard.’ It was totally empowering.”

Matt Mondanile of New Jersey indie rock band Real Estate says he learned how to play “Teen Spirit” in middle school, years after Cobain’s death. And although Weezer was the band responsible for the riffs he first fell in love with, it was Nirvana that laid bare the mechanics of rock and roll.

“I liked the idea that it was just this three-piece band,” Mondanile says. “You could hear three different things all working together to create this big, insane sound.”

That big, insane sound still seems to fascinate young people learning to play the guitar. Nayan Bhula, director of the Bach to Rock music school in McLean, Va., says young students still pour through his doors asking to learn Nirvana tunes. He’s more than happy to oblige.

“There’s that instant gratification of being able to hit the first few chords of ‘Lithium’ or ‘Smells Like Teen Spirit,’ ” Bhula says. “ But there’s still nuance to this stuff, so you can keep growing.”

That nuance is what draws so many pupils to Cobain’s guitar playing two decades after his death.

“It’s subtly complex,” Vig says of “Lithium,” a song he thinks captures the rhythmic precision that Cobain nurtured through devout practice. “He didn’t really aspire to be a muso, but he did play guitar a lot. And when Nirvana came in to record ‘Nevermind,’ they had practiced every day for six months. So they were tight. As much as people think they had a slacker mentality, that was not true.”

So keep practicing, kiddos. Because these riffs are in­cred­ibly accessible but ultimately unattainable.

“Anyone can play this stuff,” says Antonoff of fun. “But nobody can play it like Kurt Cobain.”