Courtney Barnett performs at DC9. (Kyle Gustafson/For The Washington Post)

Before you become a rock star, you must first peel yourself off the couch.

So goes the story of Courtney Barnett, a songwriter from Melbourne, Australia, who made her brilliant Washington debut at a sold-out DC9 on Wednesday night.

From beneath a brunette shag that appeared to have been last shampooed in a faraway time zone, the 26-year-old sang about boredom, lousy lovers, panic attacks and the Rolling Stones with deadpan nonchalance.

Her lyrics are funny, but it takes even greater skill to express 20-something numbness in such debilitating detail. The 12 songs on “The Double EP: A Sea of Split Peas” — Barnett’s first two homespun EPs smushed together — prove that there’s still plenty to feel while living in a state of perpetual meh.

But onstage, her drowsy tunes sounded much different, coursing with a disheveled electricity that evoked Nirvana-“Unplugged”-plugged-back-in.

Especially, during “Lance Jr.,” when Barnett sang about the intersection of rock-and-roll, pornography and sleep aids with a straight face: “I masturbated to the songs you wrote / Resuscitated all of my hopes / It felt wrong, but it didn’t take too long.”

She’s one of those great singers who can’t really sing, and she compensated for her lack of range by using her accent to bend rhymes in and out of shape and enunciating her plurals like a flat tire.

As a guitarist, she was just as resourceful. Instead of strumming with a pick, she got the job done by clanging four grubby fingernails against the strings of a Fender Telecaster, making her chords feel forceful and messy at once. And her rhythm section — bassist Andrew Loane and drummer Dave Mundy — gave the entire 45-minute set a terrific sense of locomotion, keeping everything perfectly in the pocket.

It’s easy to lose yourself in the sounds of a band this simpatico, but Barnett’s sharpest punch lines still managed to pounce out of the jangle. “Avant Gardner” — her signature tune about an anaphylactic anxiety attack — felt more a like a stand-up routine you could dance to.

The funniest couplet came during the sprawling second verse when an ambulance finally arrives to whisk her away. “The paramedic thinks I’m clever ’cause I play guitar,” Barnett sang. “I think she’s clever ’cause she stops people dying.”

Even better was the push and pull of “Are You Looking After Yourself,” a trundling garage-rock ditty that reenacts a phone call between her and her worried parents: “Are you eating? You sound so thin.”

Don’t worry, mum and dad. Your kid might be one of the greats.