"It's an anti-doomsday song in some ways," says Ryan Merchant of the duo's breakout hit.

A half-decade after meeting on Craigslist, Ryan Merchant and Sebu Simonian are enjoying a long-overdue moment of mainstream recognition as the indie-pop duo Capital Cities. The group's debut album, "In A Tidal Wave Of Mystery," was released on Tuesday (June 4) through Lazy Hooks/Capitol Records; it's an example of fortuitous timing, as their pulsating single "Safe and Sound" is finally making some noise on the Hot 100 chart (the song jumped nine spots to No. 81 on last week's chart) a full two years after its initial release. With a rollicking tempo, vocal sucker-punches and a monstrously catchy trumpet riff, "Safe and Sound" has the potential to find ubiquity on multiple formats this summer.

"It started as a little idea we came up with -- it wasn't a fully fleshed-out song, per se," Merchant tells Billboard of "Safe and Sound," which was recorded in 2011. "We noticed that, when we showed it to people, there was this unanimous feeling that there was something special about this music, and we started to develop it. It took 10 different versions before we finally came to what you hear on the radio now, where we decided to add a trumpet for the main bridge part, which I think was one of our best decisions on the song. And we brought out this vintage keyboard that provides the foundation for the song. So the song really took a long time to get right, because we knew it was such an important song for us."

"Safe and Sound" was actually pieced together before Merchant and Simonian were known as Capital Cities -- back then, the Los Angeles pair was still composing music for advertising campaigns, after Simonian posted an ad on Craigslist offering his services as a producer. Since Merchant had some jingle-writing opportunities lined up, the musicians formed a duo and eventually worked on instrumental and non-instrumental tracks for companies like Hallmark, HomeDepot and Honda.

"Commercial writing is a fun business to be in as a writer," says Merchant, "because it can actually be really creative sometimes, because they’re constantly asking you to write it in different styles… It's an interesting training ground for working on pop songs later on."

"Safe and Sound" has the makeup of three or four sugary jingles squeezed into three minutes and 13 seconds -- a dreamy keyboard hook here, a tightly composed lyric there. The song is also, like most commercial music, alluringly positive. "The song is an anti-doomsday song in some ways -- expressing the idea that every generation thinks that the end of the world is right around the corner, but it never comes to pass," notes Merchant.

After releasing a self-titled debut EP in 2011 with "Safe and Sound" as the lead track, Capital Cities signed to Capitol Records in 2012 and decided to make a go at a straight-faced recording career. The songs on "In A Tidal Wave Of Mystery" were written over the past two to three years -- all five songs on the 2011 EP are featured in the album's 12-song track list -- while production was finalized at the top of this year.

The biggest shock on the finished album is that, of the two vocal guest stars, one is Andre 3000 on the track "Farrah Fawcett Hair." "It's surprising to us, too," says Merchant. "It's the most experimental song [on the album]. We went into it with absolutely no rules. We tried to make it the most ridiculous song we possibly could. We had this middle section of the song and we wanted to get one of the most undeniably good rappers on there. We immediately thought of Andre 3000. I think it appealed to him because of its quirky sensibility."

Simonian believes that the fizzy pop track "Kangaroo Court" will be the next single from the debut album, but until then, "Safe and Sound" squarely remains the duo's focus. The song is being worked to Top 40, Triple A and rock; finally received a proper music video, directed by Grady Hall, in late April; and will be performed on "Conan" this Thursday (June 6) when Capital Cities makes its television debut. The group has peppered its "Dancing With Strangers" summer headlining tour with festival dates, including stops at Bonnaroo, Firefly and Summerfest.

Merchant says that he and Simonian are relieved that a proper debut album is finally in stores, and believes that "Safe and Sound" will keep them busy for the next few months. However, the success of Capital Cities doesn't necessarily spell the demise of their commercial music days, either.

"We put it on hold because Capital Cities has taken over completely right now time-wise," says Simonian of writing advertising music. "But I think, just for the fun of it, we may go back to writing some jingles. There’s something satisfying about areaway fast turnaround times. and breaking out of your normal shell and typical styles that you normally write in. So who knows?"