The Secret Sauce Behind Pop-Music Hits

In their new book, ‘Switched on Pop,’ two podcast hosts discuss why songs by Rihanna, Drake and others break out

Why did Rihanna and Calvin Harris’s “We Found Love” top the charts for 10 weeks? Partly because of the song’s unconventional structure, say podcasters Nate Sloan and Charlie Harding. The two examine “We Found Love”—and more than a dozen other 21st-century hits—in their book, “Switched on Pop,” which comes out Friday.

The volume borrows its title from the podcast the two 33-year-old friends began five years ago about the subtle techniques shaping today’s Top 40 hits. Mr. Sloan is a University of Southern California musicologist and Mr. Harding is a songwriter and musician who plays the guitar, drums and keyboards, as well as other instruments. Their podcast and book are filled with sophisticated but accessible discussions of pop hits from the 2000s and 2010s, from the catchy hook of Ariana Grande’s “Break Free” to Drake’s use of simple rhymes in “God’s Plan.”

In addition to offering a theory-driven take on what the authors call “the bubbliest of bubblegum pop,” the “Switched on Pop” book provides a toolkit for appreciating popular music. The authors delve into musical building blocks like melody, rhyme and sampling.

Messrs. Sloan and Harding spoke with the Journal about how streaming and hip-hop are transforming pop music. An edited transcript:

Charlie Harding, left, and Nate Sloan turned their podcast about popular music into a book. PHOTO: ELLYN JAMESON
You already have a podcast. Why a book?

Mr. Harding: Listeners were saying, “I learned a lot from the show, but I want a comprehensive guide to how to listen more thoughtfully.” That knowledge sits in music-theory textbooks. So we saw an opportunity.

Mr. Sloan: When we’re doing the podcast, we’re responding quickly to what’s happening in the fast-changing world of popular music, which is a great exercise. Forcing yourself to listen to pop makes you confront your own calcifying biases. But the book allows us to think about the things we’ve learned and put them in historical context.

There’s surprisingly little discussion of actual music in the music media. Are you guys an alternative?

Mr. Sloan: People tend to focus on the lyrics of songs and the artist’s personal life. Adding music to that discussion gives even more depth and nuance to how you can think about pop’s role in our culture. There are probably people who think Taylor Swift could release anything and it would be a hit, because of her celebrity. We’d say no. These songs are popular for a reason. You may not like that reason, but there is a reason.

Older listeners often say music isn’t as good as it was. What’s your response?

Mr. Sloan: Pop music reflects the time in which it is made and may not be as relevant to you as you age. But at the same time, what’s been revealing about doing this podcast and book is finding out how pop is changing. One thing we track is how timbre [the quality that lets us distinguish different artists or instruments] and tone are becoming such important elements of pop. Things that might have been privileged in the past—complex harmonies, lyrical creativity, guitar solos—aren’t as privileged now. That can be disorienting, but it doesn’t mean music is bad. The hope is, when you do have to listen to, say, Skrillex, you can at least say, “I don’t like this, but I kind of understand why someone would.”

Mr. Harding: It’s OK to like the things you like, but I also feel strongly that it’s not OK to think other kinds of music are outright bad. By expanding your palette of hearing, you can be more inquisitive.

Are older fans looking for things that are no longer there and then ignoring the innovation? Music, over time, becomes like a foreign language.

Mr. Sloan: I agree. It’s hard to listen to something that doesn’t follow the musical criteria we’ve established. But new music is complex in different ways.

Mr. Harding: Part of Drake’s brilliance, for example, is he is able to say something that sounds utterly familiar—as if you’ve heard it a thousand times—and yet no one has quite put those words together in that way.

Mr. Sloan: It’s a gift, being able to write those catchy nursery rhymes. The way Drake uses rhyme is masterful. One thing he does in the song “God’s Plan” is give you the same phrase, but at different points in the rhythm—keeping it fresh.

The book discusses big hits. Any recent ones you don’t like?

Mr. Sloan: A song we find vexing is “I’m the One,” by DJ Khaled. This is a song we will not redeem. We think it’s derivative, offensive and boring. And yet it was a No. 1 hit. You still have an opportunity to ask why.

Let’s talk Rihanna.

Mr. Harding: Rihanna’s “We Found Love” with Calvin Harris came out in 2011, and while it might seem like any other pop song, it’s upsetting a long-held tradition. Since the 1950s, one thing that’s stayed relatively stable is song form—the verse-chorus form of songs. What this song does is take the structure of electronic-dance-music songs, which is different, and superimpose it on pop.

Mr. Sloan: And now it’s hip-hop that is pushing the verse-chorus form to its breaking point. Take “Sicko Mode” by Travis Scott. It doesn’t have a verse or a chorus. It’s this stitched-together collage of song fragments that seems more at home in the work of an experimental composer.

Will music streaming lead to shorter, simpler songs?

Mr. Harding: The economics of streaming incentivizes songs to be shorter because you get paid per song. We’re also seeing more choruses at the start of songs to hook you in. Listeners have more choices than in the past. It’s forcing producers and songwriters to think intensely about never having a dull moment. But I think there’s always been anxiety about technological change. Songwriters have long paid attention to the medium, from the limits of the vinyl record to the CD.

Mr. Sloan: These developments always circle back to something much older. It’s easy to feel a certain panic about streaming. But “Old Town Road” is still 15 seconds longer than the shortest No. 1 hit ever, in 1960. What’s past is prologue.