Of all the great cover bands that call the River City home, perhaps the most iconic is El Monstero: St. Louis’s definitive Pink Floyd tribute band that sells out six nights at the Pageant every December.

Featuring some of the most talented musicians in St. Louis, El Monstero continues to reinvent the show year after year. The band began performing in 1999 and has grown into both a holiday and summer tradition for fans of Pink Floyd in St. Louis and the Midwest.

El Monstero started as a general classic rock cover band, however; the decision to perform a full show of Pink Floyd songs came organically. “As a four-piece band, we played around town as El Monstero,” says lead vocalist Mark Thomas Quinn. “At the end of our shows, we would add some Pink Floyd songs, which escalated into doing a whole side of ‘Dark Side of the Moon,’ then the whole album. A lot of people were waiting until the end of the show to come in and see that band. At that point, we decided to put on a show of all Pink Floyd songs and see how it went. The show was at Mississippi Nights on Nov. 27, 1999. That show sold out, and we realized we were really onto something.”

The following year, El Monstero debuted at the Pageant. “It evolved from one show a year, then two, then three, and now we do six,” Quinn says, adding the band started doing outdoor summer concerts in 2011, but the Pageant remains the band’s “home base.”

Flying by the seat of their pants on what started as a “shoestring budget,” Quinn says, “the band got more and more popular,” and the production of the shows evolved. “The production people in town realized, ‘If we want to get our production company involved, this is the hot ticket that everyone wants to see,’ so they kept upping the ante as we went along,” Quinn explains. “Here we are 18 years later, and the show is as good production-wise [including lighting, pyrotechnics and staging] as anything you’re going to see by a national touring act.”

To keep the shows fresh after nearly two decades, Quinn says, the band is always pushing the boundaries. “We’re of the age group that when you went to a show, it was a show,” he says. “I always use KISS as an example because when you went to their show, there were flames and stuff blowing up in addition to the music. You were visually stunned by it, and that’s what we want for our audience. People have always had lasers and lights, but we want to hit you over the head with how visually stunning a show can be.”

At the Pageant, the nearly three-hour production features mainly the David Gilmour and Roger Waters era of Pink Floyd, featuring songs from the albums “Meddle,” “Dark Side of the Moon,” “Wish You Were Here,” “Animals” and “The Wall.” The set list typically contains a few post-Waters numbers and occasionally a song or two from the Syd Barrett days.

“I think we’ve had a pretty good hand in helping some songs along that may not have been very big but were great songs, ‘Fearless’ being one of them,” says guitarist and vocalist Jimmy Griffin. “I think of us as curators for their back catalogue. If it were up to me, we’d play more Syd Barrett songs too.”

Griffin says backup vocalists Ermine Cannon, Tandra Williams and Coco Soul, who are mainly featured during “Dark Side of the Moon,” are “laser beams of human voices.”

“It’s always such a joy to get to sing with the girls,” he says. “If anything’s ever wrong, I know it’s me and not them — they’re just great.”

The 30- to 35-song show is an audio, video and tactile experience that complements and enhances the depth of the music of Pink Floyd. Fans can always expect a new stage production with a full cast of characters and special musical guest stars that vary from night to night.

Quinn, who also plays rhythm and steel guitar, says the music of Pink Floyd “resonates with people who think of music more cerebrally and intelligently. They don’t just listen to it on the surface but really dig deep and listen to the words, which can operate on so many different levels and take on so many meanings. It really hits people in the heart and the brain; that’s why it’s stood the test of time so much more so than a lot of other classic rock bands.”

Griffin, who joined the band in 2006 after being a guest performer the previous two years, says Pink Floyd goes down with “the Beatles and the Stones and that early music that had such an impact on the planet and society. Pink Floyd will be looked at in a couple hundred years the same way we look at Beethoven and Brahms — it’s classical music for a new generation.”

“Some of the stuff can get pretty down, pretty dire,” says Griffin, who brings “enthusiasm” to the shows. “A lot of Pink Floyd bands just kind of stand there, much like Pink Floyd does, but I see myself as more of a visual performer. I love it just as much as the audience does, and I think they get that.”

Griffin says he is inspired by the connection music offers. “I love looking out and seeing a 14-year-old kid sitting there with his 60-year-old grandfather and digging the same thing,” he says. “Part of me doing these shows is getting to be that 15-year-old kid wanting to step out in front of 2,000 people and play through three Marshall half stacks loud as balls. It’s still being in touch with that kid who wanted to learn how to play guitar.”

To prepare for each performance, Griffin says a shot of whiskey or tequila and a cough drop does the trick. “I still get butterflies, but I hate standing around and waiting to play; I’d much rather be out there. I have a little amp upstairs though, and I’ll grab my guitar 15 or 20 minutes before we go on and play for a little while just so I don’t go out there cold.”

Meanwhile, Quinn gets into a meditative state and visualizes the show to prepare. “I try to think of every minute of the show before I actually go out and perform,” Quinn says.

While production planning starts months in advance, the 12 to 15 band rehearsals don’t begin until after Thanksgiving. “When you’re dealing with eight people in a single band, it’s hard to allot that time for rehearsals, but everybody knows to block out this amount of time this time of year for the shows,” Quinn says.

Despite performing in the Lou for nearly two decades, the story behind the band’s name has remained rather shrouded in mystery for many fans. “As I recall,” Quinn begins, “the band Stir — with original El Monstero members Kevin Gagnepain, Andy Schmidt and Brad Booker — had a front-of-house sound guy named Tim Kresko who’s been running sound for El Monstero since 1999.Tim has a knack for being absurd on the road, and he would go around the dressing rooms and write ‘El Monstero was here’ as kind of a caricature of ‘Kilroy was here.’ Nobody really knew what it meant; it was kind of an inside joke for Tim. So when we formed the band, we used that moniker Tim created. The full name was actually ‘El Monstero y Los Masked Avengers’ but we dropped that last part.”

Don’t miss the best psychedelic rock concert this holiday season at the Pageant with shows at 8 p.m. Dec. 21-23 and 28-30.

For more information, visit ElMonstero.com or facebook.com/ElMonsteroM

ART: Nathan Parker | LIGHTING: Evan Endicott | MAKEUP ARTIST: Kate Clark | STYLING: Darin Slyman | CLOTHING: Lindbergh | PR: Julie Lally