A Katy Perry tour is not a simple thing.

About 18 months on the road.

More than 100 performers, technical directors and crew members.

Two dozen semi trucks.

Enough props for 300 or 400 technological cues.

Two or three sets of each costume.

And one LED bra.

Perry and her traveling circus visit Salt Lake City’s Vivint Smart Home Arena on Friday night.

Katy Perry

With Purity Ring

When • Friday, 7:30 p.m.

Where • Vivint Smart Home Arena, 301 W. South Temple, Salt Lake City

Tickets • $47.50-$147.50; Ticketmaster

But the ringmasters of “Witness the Tour” are Ashley Evans and Antony Ginandjar, a pair of Australian directors and choreographers who run a Los Angeles-based “boutique production house” known as The Squared Division.

They’re eager for the public to … well … witness their creation.

“With Katy, the good thing is that she wants to dream big, and she wants to put on a show that people will remember, and she wants to get moments that will be iconic for her for the rest of her career,” Evans said in a joint phone interview. “We wanted to create a show that people came to, and the fans — more importantly — came to and connected with and enjoyed, and got to experience the new music in a fresh way and the old music in a fresh way, but still keeping it Katy Perry. What we achieved is a show that’s very Katy, but it’s a new Katy. And I think that’s pretty exciting.”

Katy Perry performs at Wango Tango at StubHub Center on Saturday, May 13, 2017, in Carson, Calif. (Photo by Chris Pizzello/Invision/AP)

The Squared Division, who’ve worked with the likes of Taylor Swift, Britney Spears, Kesha, Iggy Azalea and Nick Jonas, began work with Perry about six months ago for the Glastonbury Festival show she did, and then some TV appearances in Australia and L.A., before landing the tour gig.

The first order of business was sitting down with Perry and her musical director, Kris Pooley, to craft a setlist around which to build the show. Then came a meeting with the singer to get her vision for the overall feel, with the new album and its accompanying designs serving as inspiration.

The result is something simultaneously retro yet futuristic.

“Obviously, the album has a bit of an ’80s theme, especially on the artwork and all the promo that she’s been doing, and the fashion she’s been inspired by has an ’80s throwback,” Ginandjar said. “So we really wanted to take the ‘Witness’ tour in a direction that felt like the ’80s, that felt like she was an ’80s space traveler.”

(Photo courtesy of Stephen Busken) Ashley Evans, left, and Antony Ginandjar are Australian directors and choreographers who run a Los Angeles-based “boutique production house” known as The Squared Division, which designed the show in Katy Perry’s “Witness the Tour.”

Evans and Ginandjar said there was no pressure to top Perry’s previous over-the-top shows, just to fulfill their creative potential and craft something audiences will appreciate.

And that is made easier given that there’s yet to be an idea presented that’s so outrageous that Perry will say no to it.

“I don’t think that would ever come out of her mouth, that something’s going too far!” Evans said with a laugh. “I think she loves to take things to a great, far place. There’s probably small things that we’ve all gone, ‘Eh.’ But they’re all topics of conversation. It’s about understanding her brain and understanding she wrote this album, she’s created this world with the music, and it’s important that we got on that same page.”

“And she’s a very brave girl,” added Ginandjar. “We have her flying around the stage in harnesses, and she’s fine up there in the air. She’s absolutely fine.”

Which is not to say things can’t or don’t go wrong. With as much technology in play as this show has, it’s practically inevitable.

At an October concert in Nashville, for instance, Perry was floating through the air, riding a replica of the planet Saturn while strumming her acoustic guitar to the song “Thinking of You.” Except, when the song was done, Saturn was stuck in orbit, and crew had to manually lower it to the floor. Then her next set piece, a shooting star, failed to appear as planned.

Ginandjar said the only thing that gives him “butterflies in the stomach” before a show anymore is the realization that, “If there’s a power failure, it all goes, you know? Or if one computer crashes, the show is stopped.”

Evans echoed the sentiment, but said that at this point, he almost takes a what-can-you-do? attitude about it all.

“Sometimes technology just has a mind of its own, sometimes it just stops working, regardless of how great it is or how much time, money, rehearsal you’ve spent on it. Sometimes things just don’t work!” he said. “If anyone can handle it, it’s Katy. She’s an easy talker, she loves to talk to the fans, and I’m sure she made that a fun moment for everyone.”

Of course, all that technology has its perks, too.

There is an LED bra, after all.

Perry is doing constant small costume adjustments onstage and complete attire changes backstage between the show’s acts. Evans acknowledged that the singer’s penchant for outlandish attire means her wardrobe is sometimes a bigger talking point than her music.

“Fashion’s important, it’s important to Katy, and it’s definitely at the forefront of this show,” he said. “I think she always tries to step it up again and again and again, and tries to create a new visual.”

Given that, Ginandjar was positively giddy about the opportunity to make fashion and tech intersect.

“She’s also got a bra that is like a screen in this show. For Act 2, she wears this LED bra, and it’s programmed to the music, and it syncs up with the lighting desk, and it talks to the lighting desk so we can tell the bra what to say and what to do; if we want it to have words on it, we can make it have words on it,” he exclaimed. “It’s very ahead, and again, technology is amazing! We can put technology into a bra!”

In the end, both reiterated the importance of the many people involved in pulling it all off.

“It’s a giant machine of people that are just working around the clock to make these shows happen,” Evans said.

He added that the entire production team and touring staff have a litany of details to take into account that the average fan will simply take for granted.

“We need to understand, can the set actually fit in the venue? Can things that we fly in the air actually fit? Is the ceiling high enough? If we do hang people up there, are they going to obstruct people’s views? How big the loading doors are. Do we have enough storage space backstage to get these props in and out? The weight of things. This stage is so big that the actual screen — which I’ve never seen [this] before — actually cuts into the seating area. So we have to make sure that these are going to fit into every venue,” Evans said. “There’s so many technical things. Are these props gonna last being packed down and unpacked every show? We have to make sure that all the props are made to a standard that doesn’t allow them to break down after three shows. Things have to last. Costumes — the choice of fabric needs to be clever. If you choose a certain type of fabric, it’s not going to last much more than a month, and it needs to last 18 months. So we have to make sure we get two or three sets of each costume made. The thought process, when touring for 18 months, it’s definitely about, ‘Is it gonna last?’ ”

Ginandjar equated getting everything to fit in the trucks and the venues to a jigsaw puzzle and a Tetris game.

All that effort is worth it, he said, when Perry’s fans react to the spectacle.

“It’s a show I think we’re all proud of and that the audience are really responding to, which is lovely to see,” Ginandjar said. “What a lovely experience it has been for Ash and I to work on this show with Katy. And we just hope that everyone enjoys it as much as we have. Let’s hope everyone in your city loves it!”