The wide-ranging interview with the two songwriters covers everything from Tranter's unreleased work with Lady Gaga to who is on their wish list of collaborators (Beyoncé! Taylor Swift! The Killers!).

Welcome to the new episode of the Billboard Pop Shop Podcast, your one-stop-shop for all things pop on Billboard's weekly charts. In addition, you can always count on a lively discussion about the latest pop news, fun chart stats and stories, new music, and guest interviews with music stars and folks from the world of pop.

Casual pop fans and chart junkies can hear Billboard co-director of charts Keith Caulfield and Billboard music editor Jason Lipshutz every week on the Pop Shop Podcast, which can be streamed on Billboard.com or downloaded in iTunes ( click here to listen to the previous Tuesday’s edition of the show on Billboard.com).

On the latest show, we have a special edition of the podcast dedicated entirely to a lengthy — and super fun — interview with songwriters Justin Tranter and Leland. The pair has separately helped craft songs for acts ranging from Selena Gomez, Imagine Dragons, Daya, Justin Bieber, Troye Sivan, Fall Out Boy and Allie X.

In our wide-ranging chat, we discuss a bevy of topics, including Tranter and Leland’s recent work with Gomez — as Tranter co-wrote “Bad Liar” while Leland co-wrote “Fetish.” We dive deep into how Leland and his songwriter partners specifically composed “Fetish” for Gomez, how the song got to her, and how Leland ultimately found out it was going to be a single (from a surprising source).

“I'm such a massive fan of her and the music,” Leland says of Gomez, who was inspired to write a song for the pop star after loving her last album, Revival.

“I've been working with the same (team of songwriters) for the past four or five years,” says Leland, “and I sort of organized two weeks where all we did was ideas for Selena. The ultimate goal for me would be a Selena cut. So we sorta banded together for two weeks and started coming up with a lot of different ideas, and at the end of the two weeks we looked at everything and 'Fetish' … was the standout idea.”

As it turns out, “Fetish” wasn’t the original name of the song. Initially it was called “If I Were You,” because, as Leland says, “we were nervous about it being too much, you know?” Ultimately, “it was Selena who ended up changing it to ‘Fetish,’” says Leland, “which I was really happy about.”

“The rollout (for Gomez’s forthcoming album) has been so incredible,” Leland tells Billboard, “I am just in awe of the music that she's been putting out. I feel really grateful to be a part of, I think, some of the best moments for her musically. It's incredible."

“Her taste is impeccable,” Tranter says. “She's like the ultimate… and her and Aaron Bay-Schuck (president of A&R at Gomez's label, Interscope Records) make this dream team. The A&R/artist dream team. The coolest taste, wanting to push every boundary possible. Not being afraid to push boundaries… I think Selena pushes more boundaries on pop radio than almost anybody.”

Also on the podcast, Tranter talks about how he reconnected with his old pal Lady Gaga (who once opened for his former band Semi Precious Weapons many years ago) to write some still-unreleased new tunes, how he’d “rather die” than release his own solo album, and how he’d love to work with Beyoncé, Stevie Nicks, Tina Turner and Cher. (As for Leland, his wish list includes Taylor Swift and The Killers.) Plus, Tranter recalls how DNCE’s frothy “Cake By the Ocean,” which he co-wrote, came after a week of frustration in the studio.

“I'd worked with Joe (Jonas, of DNCE) for a week,” Tranter says, “and we were kind of all taking ourselves too seriously… The next day I went in, and (told Joe) 'I think we need to be fun. You're a fun guy. You're fun and you're fuckin' hot… Of course he's a multi-dimensional human who has lots of things to offer, but, in that moment I was like, 'let's just go where you are.' … The point being, it's about getting that honesty, even if the honesty is cake by the fucking ocean, which is ridiculous. In that moment, that was the way to get to Joe's core.”

Meanwhile, Leland — who is busy writing new tunes with Sivan — is also embarking on his own solo artist career, having recently released his single “Mattress.” The track has earned over 1 million on-demand audio streams in the U.S., according to Nielsen Music.

Was it always Leland’s goal to be both a songwriter and solo artist? Why now for his artist project?

“It's because I realized I'm completely comfortable with myself,” Leland says. “Two years ago I was not there yet. Three years ago I wasn't there yet. It could be a year ago that I necessarily just wasn't there to sing about boys, say exactly what I wanted to say, sing the lyrics comfortably… It feels right now. It also feels right because the resources are there. The friendships are there. And the desperation isn't there. Two years ago I felt like I just didn't necessarily have the resources and I felt desperate to become an artist. And I hit a wall, I guess, where I was like this doesn't feel right, and I shifted my focus and energy to writing for other people and doors flew open. Now, approaching my artist project this time, it feels really -- not easy -- but it feels right. It feels beautiful.”

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