Sarah Gardner: Remember this song?

Adele, “Rolling in the Deep”: There’s a fire starting in my heart.

Isn’t that just so July 4, 2011? As is now typical with Top 40 radio, you hear Adele’s “Rolling in the Deep” every once in a while, sort of a nostalgic throwback to, well, last summer.

So what’s rocketing up the charts right now? And what makes a Top 40 hit into a No. 1 summer blockbuster? Marketplace’s Mitchell Hartman got the beat on that one.

Mitchell Hartman: Unless you only listen to the kind of radio we produce here at Marketplace, you have probably heard this song at least once in the last, oh, I don’t know, 59 minutes?

Carly Rae Jepsen, “Call Me Maybe”: Hey, I just met you, and this is crazy, but here’s my number, so call me maybe.

Canadian waif-pop-singer Carly Rae Jepsen soared out of obscurity this spring with her bouncy love song “Call Me Maybe.”

Silvio Pietroluongo: The forecast is she may remain at the top of that summer list.

That’s Silvio Pietroluongo, director of pop charts at Billboard magazine.

Pietroluongo: There is some competition there, so I’m not going to say the race is over. But she’s got a great head start.

And who’s nipping at Carly Rae’s heels? Pietroluongo puts the odds on Maroon 5 and their hit, “Payphone.”

Maroon 5, “Payphone”:  I’m at a payphone, trying to call home, all of my change I spent on you.

Pietroluongo also likes “Where Have You Been” by Rihanna and “Wide Awake” from Katy Perry.

Pietroluongo: You know, right now we’re at an up-tempo dance pure pop phase. A few years ago, it was really hip-hop and some R&B songs, so everything has its cycle and right now, we’re at a pure pop cycle.

The cycle itself — that’s also a big part of the formula, the same songs every hour in rotation.

Brett Andrews: All right 2 o’clock, Brett Andrews radio show checking in with Maroon 5, Wiz Khalifa on the way, Katy Perry.

Brett Andrews is program director and afternoon DJ at Z100, a Top 40 station in Portland, Ore.

Andrews: It is very formulaic, we do have numerical systems in place. The most important thing for us is familiar, familiar, familiar. People like to tune on the radio and hear a song they can sing along to.

But in the case of Carly Rae Jepsen, Americans had barely heard anything from her. Then she got some big assists: Justin Bieber and Selena Gomez lip-synced a tribute video to her song, and it went viral.

Andrews: Even former Secretary of State Colin Powell was caught on-camera singing that song. It’s moved away from just being a fun little pop song, to being this viral, kind of cultural identifier for the summer.

And me? I like a song called “Drive By” by the post-grunge rock band Train.

Well, I like underdogs. Right now, they’re holding at Number 19 on the pop charts.

I’m Mitchell Hartman for Marketplace.