This article is Part 2 of a multipart series looking at the statistics gathered from 1300 choruses, verses, etc. of popular songs to discover the answer to some interesting questions about how popular music is structured. Click here to read Part 1.

In Part 1, we used the database to learn what the most frequently occurring chords are in popular music and also started looking at the likelihood that different chords would come after one another in chord progressions.

In Part 2 of this series, we’ll continue this exploration into the patterns evident in the chords and melody of popular music. First we’ll look at how popular music ends musical ideas and discuss a surprising difference between popular music and classical music. Then we’ll talk about the most popular chord progression used by songs in the database and discuss the ubiquity of this progression. Finally we will revisit the question of “which chords occur most frequently in popular music” and look at the reasons for why this is the case.

The first article received A LOT of really great feedback. We’re definitely using the feedback you’re giving to help guide us with where to go next, so keep it coming. Let’s get started with Part 2.

1. What are the most common ways that songs written in C get back to the C major chord?

For songs written in C major, the C major chord (the I or “one” chord in Roman numeral notation) is the song’s tonal center, so this is an important question to explore.

Probably the most fundamental rule governing chord progressions in classical music is the idea that in the key of C, G major chords (or V chords) are the right way to wrap up a musical idea. This has been known for ages, and popular music would be expected to do this too. Listen to this section from “I Don’t Want To Miss A Thing” by Aerosmith. As the clip plays, we’ve highlighted the chords for you to follow as you listen along.

Listen in particular to that final G chord at the very end of the crazy buildup. That’s a V chord. And that’s how you end chord progressions. That’s just how it’s done.

“I Don’t Want To Miss A Thing” by Aerosmith

…Except when it’s not. One of the interesting things about popular music is that this V → I (G to C) resolution isn’t adhered to nearly as much as it is in classical music. How much does popular music depart from this standard? We can answer that by looking at the songs in our database to get a precise answer. The following plot shows the frequency that the other basic chords are used to come before I (C for songs written in C).

Chords right before C major (the I chord)

What stands out here, is that IV → I (F to C) is not only normal, it actually shows up just as often as V → I (G to C). This is surprising (at least to a classically trained person).

We also learn from this data that very few chord progressions go from iii to I (Em to C). In Part 1, we learned that Em (iii) almost always goes to F or Am (IV or vi) so this is totally consistent. Some of you were interested in seeing examples of songs that break with the trends that we’re finding. In that spirit, here’s one song in the database that happens to use Em (iii) in this way: Lady Antebellum’s “I Need You Now”:

“I Need You Now” by Lady Antebellum

This illustrates the point that it’s definitely possible to “break the rules” and still sound great. If you’re tempted to take this as an invitation to just experiment and do whatever you want, just remember the old mantra that I wish more songwriters would follow: “You’ve got to learn the rules before you can break them”. In fact, in this very example the weaker iii → I (Em → C) only happens in the first phrase. In the second repetition, the verse is ended much more emphatically with a strong G going to C (V → I). Also notice that the beginning of this section starts on a C (I) chord that is arrived at from an F (IV). So while this song uses the iii in an unusual manner, it is still following a lot of other “rules” elsewhere.

2. What is the most popular chord progression used by songs in our database?

To answer the question many of you were asking in the comments. The most popular four-chord progression that shows up in the database is in fact the I → V → vi → IV (or C → G → am → F in the key of C). This, by the way, is a great example of a progression that uses the IV instead of V to get back to I. You can listen to a few songs that use this progression below:

“Don’t Stop Believing” by Journey (1981) “Let It Be” by The Beatles (1970) “She Will Be Loved” by Maroon 5 (2002) “Edge Of Glory” by Lady Gaga (2011)

What to take away from this? First, let’s be clear that just because a song uses only four chords doesn’t mean it’s necessarily stupid or inferior. It’s how you use those four chords that counts. Even more importantly though, I want to dispel the notion that popular music can’t be interesting musically.

Even though it’s true that there are a lot of songs that stick to just four chords, this definitely isn’t universal. There’s lots of examples in “popular” music that are really rich harmonically. To give just one example, listen to the chorus from the song “Who Says” by the John Mayer:

“Who Says” by John Mayer

John Mayer songs are often interesting to analyze because he studied at the Berklee School of Music and knows his harmony. This is the type of chord progression that a classical musician would recognize and understand immediately.

But popular music also uses chords in ways that are different from what a purely classically trained musician would be accustomed to hearing. Consider Christina Aguilera’s “I Turn To You”:

“I Turn To You” by Christina Aguilera

There’s obviously a lot going on in this song harmonically, and while I’m sure you guys will analyze every detail in the comments, the point I’m trying to make here is that there are examples of interesting uses of chords in popular music everywhere. You just have to look for it.

3. “Why” are the most frequently used chords in popular music what they are?

In part I, we found out that the most commonly occurring chords were the following:

Chord use when all songs are transposed to the key of C major

The reality is, and this was pointed out by many of you in the comments, that a lot of the explanation behind all of this can be answered with some basic music theory. If you’re interested in learning some of the reasons that these chords are popular, we encourage you to check out Hooktheory I, our interactive book for iPad and web that teaches the theory behind popular music in ways that are approachable and fun to all musicians. Thank you for reading! Let us know what you think in the comments below.

Other posts in the 1300 song series