British synth-pop group Depeche Mode. Picture: Depeche Mode/Instagram

An old New Wave rock band that's never released a No. 1 song in the U.S. is selling more concert tickets than the biggest pop stars in the world.

Depeche Mode, the British synth-pop group formed in 1980, is having one of the most remarkable tours in modern music and its most-successful concert run ever. The band sold 1.27 million tickets through the first nine months of 2017, more than Ed Sheeran, Justin Bieber or Bruno Mars -- much younger pop acts at the peak of their fame.

In October, the band became the first act to sell out four consecutive shows at the Hollywood Bowl, an open-air theater in the hills of Los Angeles that's hosted everyone from the Beatles to Luciano Pavarotti. 

Now Depeche Mode is back on the road for its second tour through Europe this year and will head to Latin America in 2018. Not bad for a group whose album sales peaked more than 20 years ago.

"Every time we go out and tour, we're playing to more people," said Martin Gore, 56, the band's guitarist and lead songwriter. "It's just incredible at this stage in our career."

Depeche Mode's success speaks to the enduring power of old rock groups, which accounted for a big chunk of the $7.3 billion North American concert industry last year. 

The best-selling festival of 2016 was Desert Trip, a bacchanal in California's Coachella Valley featuring acts that came to prominence half a century ago. According to researcher Pollstar, the top tours of 2017 are Guns N' Roses and U2, which released their best-selling albums 30 years ago.

Yet Depeche Mode's late-career surge is also a tribute to a band that has carefully nurtured and expanded a loyal army of fans known as the Black Swarm (or Devotees) who follow it all over the world. The mania for the group's dance pop is strongest in Germany, where the last seven albums have topped the charts, but it reaches every corner of the globe.

The group has never stopped touring, even during a drug-addled era that manager Jonathan Kessler dubs "the experimental years." Lead singer Dave Gahan, whose distinctive baritone is one of the band's signatures, has grown more confident as a performer with each tour, strutting across the stage like a man possessed. 

Where the band once struggled to sell more than a couple thousands tickets in Nashville, Tennessee, it now plays before crowds more than triple that size in the cradle of country music.

Periods between tours give band members time to recharge and leave fans wanting more, especially because the group doesn't venture to the same cities every tour. Salt Lake City was the first stop on the 2017 U.S. tour, a place that hadn't hosted Depeche Mode since 2009. 

Eight years is also enough time for devotees to inculcate their children with a love of songs like "Personal Jesus" or "Enjoy the Silence."

Depeche Mode doesn't sell records like it did in the 1990s, nor has it ever reached the heights of fellow British rockers Coldplay or Oasis. But a group whose musical genre was once derided has earned long-overdue respect. Critics raved about the latest tour, while Marilyn Manson, Trent Reznor of Nine Inch Nails and Rihanna all cited the band as a major influence.

While Metallica and Taylor Swift have fought new ways of distributing music, Depeche Mode is yet to embrace new technologies, be it Apple's iTunes or Spotify. Inspired by the Grateful Dead, which allowed fans to make their own recordings of live shows, Depeche Mode has often fought its record label and publisher to leave unlicensed videos on YouTube.

Searching for the proper way to promote this latest tour, Depeche Mode opted to let a different fan take over its Facebook page every day to share stories and photos. Facebook is an ideal medium for Depeche Mode, whose core audience is between the age of 35 and 60. Fans have already created more than a dozen different fan pages and groups for Depeche Mode on the social-media platform.

This project gave those fans control of the band's official page for the first time. Devotees from all over the world have shared their favorite memories, including some who say they've seen the band more than 40 times just this year. The page has 7.3 million "likes."

While a single TV advertising campaign would cost millions, the Facebook promotion is free.