RACHEL MARTIN, HOST:
What makes a song a hit? Is it a catchy beat, an amazing voice? Let's use this song as an example.
(SOUNDBITE OF SONG, "SHAKE IT OFF")
TAYLOR SWIFT: (Singing) 'Cause the player's gonna play, play, play, play, play. And the hater's gonna hate, hate, hate, hate, hate. Baby, I'm just gonna...
MARTIN: That is Taylor Swift's "Shake It Off." You've probably heard in a million times or so. But what makes it so popular? Joseph Nunez is the lead author of a new study that looks at thousands of hit songs from the past 50 or so years. And he has the answer.
JOSEPH NUNEZ: Songs that are more repetitive do better.
MARTIN: Repetitive?
NUNEZ: Yep. The more times you sing a chorus, the better the song will do in the charts.
MARTIN: It's true. I got to say, I have danced to my fair share of "Shake It Off" in my living room.
NUNEZ: Of Taylor Swift, right.
MARTIN: So in a separate study, you looked at the instrument and vocal combinations that can make a song successful. So what did you find there?
NUNEZ: Well, the big thing is background vocals. So if you have background vocals, a synthesizer and a clean guitar...
MARTIN: What do you mean by clean guitar?
NUNEZ: If you take an electric guitar, it has all kinds of different sounds. The cleaner the sound is, the less distortion that you have.
MARTIN: OK.
NUNEZ: So take a song like Madonna's "Papa Don't Preach."
(SOUNDBITE OF SONG, "PAPA DON'T PREACH")
MADONNA: (Singing) Papa, don't preach. I'm in trouble deep. Papa, don't preach. I've been losing sleep. But I've made up my mind, I'm keeping my baby.
NUNEZ: Background vocals also help us want to sing-along. Songs that are more repetitive get listeners in pop music to want to sing-along and want to repeat the chorus with you.
MARTIN: Is there such a thing as too much of a good thing? I mean, are there songs out there that repeat way too much and then we stop listening?
NUNEZ: I think so. But that didn't happen in our data. So once you got on the hot 100, the more you repeated the chorus, the more word repetition, the less complex the song, the better it did.
(SOUNDBITE OF SONG, "ALL ABOUT THAT BASS")
MEGHAN TRAINOR: (Singing) Because you know I'm all about that bass, 'bout that bass, no treble. I'm all about that bass, 'bout that bass, no treble. I'm all about that bass, 'bout that bass, no treble. I'm all about that bass, 'bout that bass, bass, bass.
MARTIN: There have to be some outlines in all of this, right - songs that didn't have any of these characteristics, but still did really well? What's an example in that camp?
NUNEZ: Well, one that stands out is Lionel Richie's "Truly."
(SOUNDBITE OF SONG, "TRULY")
MARTIN: Great song.
NUNEZ: Great song.
(SOUNDBITE OF SONG, "TRULY")
LIONEL RICHIE: (Singing) Girl, tell me only this.
MARTIN: (Singing) 'Cause I'm truly - sorry, I digress.
NUNEZ: Oh, no problem.
MARTIN: (Laughter).
NUNEZ: Can you remember any of the lyrics of the song?
MARTIN: No (laughter).
NUNEZ: It's because he only repeats the chorus one time. Yet he soared to number one.
(SOUNDBITE OF SONG, "TRULY")
RICHIE: (Singing) ...Because I'm truly, truly in love with you girl.
NUNEZ: There's also songs that have lots of repetition that never even made it to number one.
MARTIN: Yeah. So what's an example of a song that supposedly has all the right ingredients, but just doesn't do well.
NUNEZ: 1977, Van Morrison's "Moondance" repeated the course more than six times, but yet he never made above number 90.
(SOUNDBITE OF SONG, "MOONDANCE")
VAN MORRISON: (Singing) Well, it's a marvelous night for a moondance with the stars up above in your eyes.
MARTIN: Joseph Nunez is a professor at the University of Southern California. Thanks so much for talking with us, Joe.
NUNEZ: Oh, I enjoyed it. Thank you, Rachel.
(SOUNDBITE OF SONG, "MOONDANCE")
MORRISON: (Singing) You know the leaves on the trees are falling to the sound of the breezes that blow. And I'm trying to please to the calling of your heart strings that play soft and low.