Washington DC - March 14: Portland band The Mean Jeans performs at Burger Records Fest, an Unofficial SXSW (South By Southwest Festival) show at Trailer Space Records in Austin. (Josh Sisk/FTWP)

The guitars squeal. The bass grumbles. The drums feel like bully punches. It’s Wednesday night, and a hundred-ish young fans have crammed into Trailer Space, a record store in East Austin, to hear the Seattle trio Night Beats.

One fan cradles a collie in his arms like a waltz partner. When someone lights a handful of firecrackers near the stage — TAT-TAT-TAT-TAT-TAT! — the dog remains unfazed, tongue lolling.

Run, Lassie! Go tell the others that rock-and-roll is still alive in Texas!

Since 1987, thousands upon thousands of fans have flocked to South By Southwest each March in hopes of discovering their favorite new bands. Now in its 26th year, the annual music festival has metastasized into a branding circus where corporations scramble to attach themselves to the cred of artists who already have established their cool online. This year, the festival is hosting a few superstars who have presumably flown to Texas with similar intentions — Jay-Z, Bruce Springsteen and Lil Wayne among them.

But through rosier-colored Wayfarers, SXSW is still the best place on Earth to renew your vows with rock-and-roll. You just have to know where to look. Trailer Space and Beerland, a grimy downtown club, have booked scores of high-energy, little-known rock bands from all across the country, none of which seem to have trekked to Austin for their big break.

“It’s just like a vacation,” says Liz Liles, drummer of Sacramento foursome G. Green. “There’s no point of trying to get famous from it anymore.” Frontman Andrew Henderson butts in, saying he came to SXSW “to party, to have fun, to play with cool bands, to eat barbecue and regret it.”

And that slouching sense of anti-ambition feels completely detached from most 21st-century major-label rock music — the chest-puffing Shinedowns and Chevelles that have made so many fans feel as if the genre is doornail dead.

But SXSW reinforces the idea that vital rock-and-roll is still with us, even if it has regressed to its murky, primordial state. The most exciting rock bands gathered here in Texas recall the golden age of garage rock captured on “Nuggets,” the influential compilation album of ’60s psychedelia assembled in 1972 by Elektra Records founder Jac Holzman and guitarist Lenny Kaye. Four decades later, these bands are delivering a similar cocktail of mischief, desperation and fun. They embody a sort of rock-and-roll invincibility — the invincibility of cockroaches.

On an early Wednesday afternoon at Beerland, G. Green’s endearing guitar scuzz inspires golf clapping from an audience of 14 who seem to be pacing themselves for the noisy hours ahead. Next up is Cruddy, a punky three-piece outfit from Austin whose fast, claustrophobic music gives the impression of a band heroically attempting to squeeze too much song into too little time. Later, Puffy Areolas frontman Damon Sturdivant closes the Ohio band’s squalling, psychedelic set by lodging his guitar into the ceiling while Indiana’s Apache Dropout set up out on the Beerland patio and howl into the cosmos, stopping a few dudes biking down Red River Street in their tire tracks.

SXSW is friendly to the scrappy. Most of these bands will play six to eight sets over the course of the festival at about 20 minutes a pop, often using a backline of amps and drums provided by the venues. Sometimes that’s for the better.

“They’ve actually been better than my own amps,” says Jessie Clavin, the guitarist of Los Angeles quartet Bleached. “I’m stoked to have, like, working reverb!” Twenty minutes later at a club called Hotel Vegas, Clavin and her sister Jennifer sing their fist-pumpable “Searching Through the Past,” guitars shimmering atop the song’s delicious, lovelorn crunch.

Over at Trailer Space, the backline is a little more rough and tumble — along with everything else. Aisles are littered with crushed beer cans. End caps are brimming with new vinyl LPs and cassettes from OBN IIIs, Mind Spiders and other bands booked to play Austin later this weekend. Outside, the store has rented a phalanx of portable toilets to keep show-goers from relieving themselves in the yards of the surrounding residential neighborhood, as they did last year.

A clerk behind the counter grabs a megaphone and announces that the Mean Jeans are up next, a Portland trio who sound like the Ramones with a colony of fire ants dumped down their boxer-briefs. Their music provokes fans to spray cans of beer on one another like hoppy holy water.

The scene is mellower earlier in the day when John Wesley Coleman offers up a clutch of clumsy-sweet power-pop tunes covered in a moss of distortion. From behind a pair of oversize sunglasses — not unlike the shades Biggie Smalls is wearing on drummer Julia Hungerford’s T-shirt — Coleman yelps about partying with his psychiatrist and girls who won’t answer the phone.

A fan noshing on a hamburger throws hunks of his lunch into a ceiling fan overhead. The spinning blades bat pieces of bread and beef across the room. After a few tunes, another guy shouts, “What are you guys called?” Coleman free-associates a dozen words, none of which are “John,” “Wesley” or “Coleman.”

He closes the set with “Where Did My Friends Go?” Its final verse offers a shrug-to-keep-from-crying rejoinder: “I don’t know! Rock-and-roll!”

After the set, Coleman lugs his amp out into the balmy Texas air and tosses it into the trunk of his beige Lincoln Town Car, which is covered in bird poop. He wishes he could stick around and hang out, but he’s working shifts at a local pizzeria this week.

“It’s like being out on tour but not having to leave,” he says of being a local act at SXSW. “The only exception is that you still have to work your job.”

With more shows and more shifts in the days ahead, Coleman’s approach to SXSW translates into a pretty good philosophy for rock-and-roll itself: “It’s a balancing act of kidney, liver, heart and brain.”