The shakeout that is rattling the music business is turning up some unlikely survivors: roadies, the black-clad backstage grunts of live shows.

“I know musicians who play on the road who make less money than the tech guys I know,” says Jimmy Davis, the stage manager for country singer Hank Williams Jr.

Roadies’ elevation to “concert technicians”—the term many practitioners favor—is reshaping their culture. Sex, drugs and rock ’n’ roll are out; efficiency, tech skills and professionalism are in. “We’re the Marines of the music business,” says Tom Weber, who got his start filling in for an absent roadie at a Kiss show 40 years ago.

Now 57 years old, Mr. Weber is one of many roadies who have converted a one-off gig into a career. In a good year, Mr. Weber, who lives in Kentucky, earns about $200,000—a princely sum for a nonprofessional job. He is in demand, with high-profile artists such as the Cult’s Billy Duffy balking at touring without him.

Mr. Weber has maintained guitars for Van Halen, Poison and Nine Inch Nails as well as country stars Reba McEntire and Lyle Lovett. Before each show he restrings nearly every guitar and says he has “never had an artist break a string on stage.”

One typical roadie job—sound engineering technician—pays $57,000 a year, on average, according to the Bureau of Labor Statistics. (The figure doesn’t take into account the legion of roadies who are self-employed.) Surveys by the Berklee College of Music say a “front of house” live-sound engineer—the person who controls what concertgoers hear—earns at least $60,000 a year, and can top $120,000. Road managers can earn $125,000 or more. Tour coordinators? $175,000.

The ascent of the concert technician reflects a seismic shift in the economics of the music industry. As concerts and festivals increasingly become a vital source of profits, cultural “middlemen”—label executives, talent scouts and other traditional tastemakers—are losing clout, experts say. Technical middlemen—artist managers, concert promoters, festival organizers, and social-media promoters, as well as DJs and roadies who mix sound at shows—are gaining it.

ODES TO ROADIES

Musical acts over the years have written songs about their road crews. Here are five classics.

‘Alan’s Psychedelic Breakfast,’ Pink Floyd (1970)
This whimsical 13-minute song features the sounds of a roadie, Alan Styles, preparing and eating his breakfast, with the band playing in the background.

‘Tonight’s the Night’ Neil Young (1975)
Mr. Young dedicated this song, which opens his album of the same title, to Bruce Berry—a roadie who died of a heroin overdose.

‘The Load-Out’ Jackson Browne (1977)
“They’re the first to come and last to leave, working for that minimum wage,” Mr. Browne sings on this ode to concert workers, which appeared on his “Running on Empty” album. “Load-out” is jargon for tearing down and packing up a stage.

‘Road Rats’ Alice Cooper (1977)
The soundtrack of the 1980 film “Roadie” featured Cheap Trick, Pat Benatar and Alice Cooper—who contributed “Road Rats.” Teddy Pendergrass, Hank Williams, Jr., and Blondie also contributed to the soundtrack. Its tagline: “Bands make it rock, but the roadies make it roll.”

‘(We Are) the Road Crew’ Motörhead (1980)
Lemmy Kilmister, the larger-than-life leader of metal band Motörhead, was once a roadie himself. His boss? Jimi Hendrix.
That makes bands increasingly reliant on live performances to make money, spurring demand for stage hands, instrument techs, sound mixers, lighting specialists and tour managers. The physical labor needed to erect elaborate, high-tech stages has spared most roadies. Their jobs can’t be moved to China or be done by a robot—at least not yet.

“Employment opportunities in the live-music industry have never been better,” says Gary Bongiovanni, the editor of Pollstar, a trade publication. “While record-company jobs have nearly disappeared, road- and tech-production-crew gigs continue to grow.”

It’s hard to pinpoint how many people work in the music industry because many of them toil in ancillary areas, such as promotion or transportation, that support artists. Federal surveys don’t track the industry’s scores of part-timers and freelancers.

The North American concert industry was valued at $6.2 billion in 2014, Pollstar estimates, up from $1.4 billion in 1994. Multiday festivals such as Coachella, Bonnaroo and Sasquatch! are flourishing, generating jobs to handle setup, security and operations.

Two years ago, Gavin Rossdale, a singer and guitarist in the rock band Bush, hired Mr. Weber for a gig. Before working with Mr. Rossdale, who is married to singer Gwen Stefani, Mr. Weber spent a week reading a 201-page manual for the Fractal Audio Axe-FX II, a complex guitar-effects system Mr. Rossdale wanted to use. To learn the ins and outs of the $2,300 system, Mr. Weber eventually bought one of his own.

“You have to know your stuff,” says Dick Adams, 69, a production manager for Metallica, Pearl Jam and Heart. A big part of the job is keeping up on the latest toys for musicians, he says. “You have to do a lot of reading.”

Despite the enduring caricature of roadies as tattooed guys with beer bellies in heavy-metal T-shirts, today’s concert hands often resemble computer geeks—and many of them are women.

“There are a lot of women in all kinds of positions—not just wardrobe and catering,” says Meg MacRae, 44, a tour manager and production coordinator who has worked with Bon Jovi and Neil Young. On a recent arena-size tour, she counted eight women among 60 crew members.

Ms. MacRae’s main job is putting out fires that inevitably erupt as her crews adapt to different venues. In between 18-hour days, she relaxes with yoga. Her only regret about her career: She and her longtime boyfriend haven’t had children. “I chose to marry the road,” she says.

The occasional brushes with celebrity and other flashes of glamour aside, working concerts isn’t for everyone. The job means extensive travel, which can be hard on relationships, and it often exacts a physical toll, including hearing loss. The flow of assignments can be irregular and the hours long and unpredictable. Roadies often earn a flat fee for a day’s work, whether it runs for four hours or 14.

Glen Rowe of Cato Music Ltd., a U.K.-based tour-production company that handles shows for bands such as Haim and Bastille, estimates that on a typical, arena-size tour, the average wage for crew members is around $450 a day. Entry-level crew members can earn around $200 to $275, Mr. Rowe says, though with experience, that can climb to as high as $1,500 a day.

Concert workers today are more likely to be foodies than junkies, says T.J. Hoffmann, a onetime roadie for Agnostic Front and Skid Row. He is making a documentary about “America’s last blue-collar army,” as he calls his colleagues. Crew members on a European tour don’t spend their days off “drinking and doing drugs,” the 45-year-old Mr. Hoffmann says. “They’re going to the Louvre.”

Harley Zinker, who just wrapped up work on three Interpol concerts in Mexico, says, “I don’t think we drink or do nearly as many drugs as people in finance do.” He started working two decades ago in New York City clubs. Nowadays, Mr. Zinker, 45, handles sound for performances by the Killers, the Strokes and others. He earns enough to take six weeks off between tours and put a chunk of money away for retirement. “It’s a very viable career,” Mr. Zinker says