I-IV-V Chord Progressions (aka "the Three-chord Trick")

I can't think of a better way to kick-off a songwriting blog than with a look at the "three chord trick". It turns out that just three chords, known as the I, IV and V chords, are the fundamental building blocks of nearly every genre of popular music, from rock and country to reggae, gospel and more.

With just these three chords a musician can play thousands of songs in various genres, but more importantly for our purposes, these three chords give songwriters a full harmonic palette with which to create new songs.

Finding the I-IV-V Chords

The I chord is always the major chord named after the key you're in, so in the key of C the I chord is a C chord, and so on. The IV and V chords are major chords built on the 4th and 5th notes of the major scale. In the key of C these chords are F and G.

If you don't know all of your major scales, here's a chart of I-IV-V in every key.

Why the Three-chord Trick Works

There are a few reasons why the three-chord trick works.

1. Every note in the major scale is contained in either the I, IV or V chord (some notes appear in more than one chord). This means that any note in a key can be effectively harmonized using only these three chords.

2. Moving from one chord to another whose root is a perfect 4th higher (going from a C chord to an F chord, for example) is one of the most powerful movements in Western music. The I, IV and V chords give a songwriter two different opportunities to do this. Both the I to IV and the V to I chord changes meet this criteria, so a progression can both move away from the I chord and return to it using perfect 4th root movements.

3. Most importantly: each of the three chords has a different function within a key, which a songwriter can use to his advantage:

• I is known as the "tonic". It is "home". You'll want to go to other chords during a song, but it always feels like the progression wants to return to I. When a song section (verse, chorus, etc) ends with the I chord it feels complete, or "closed". You can end a song on the I chord and it will sound right. Ending a song or section with IV or V sounds unfinished, or "open".
   
• IV is the "subdominant". Going from I to IV feels comfortable. It's a step away from home, but not a drastic one. From here it feels like you could go back to I if you want to, but the thought of going out and exploring some other destinations isn't particularly scary either.
   
• V is the "dominant". It's a big step away from home, and when you get here you really feel like you want to go back home. In fact, the V chord wants to resolve to the I chord so much that the V to I chord change is one of the strongest (if not the strongest) chord changes in popular music. Ending a song section with the V chord creates a very strong "open" feeling, which you can use to propel a song forward into the next section.
   

Used skillfully, the I, IV and V chords enable changes that are driving, such as V to I, or more subtle, such as I to IV. You can meet listener expectations by going in the direction of the chord's natural tendencies, or create tension by going a different way. In general, the I, IV and V chords want to move as follows:

• I wants to go to IV. You can surprise the listener by going to V instead.
   
• IV can go either way, back to I or ahead to V. Going back to I keeps things calm and stable, while going to V builds tension and listener expectation.
   
• V wants to go to I. As mentioned previously, this is the strongest chord change you have to work with. When a listener hears the V chord, he expects the next chord to be I. As a songwriter you can satisfy that expectation, make it stronger by staying on the V chord longer, or surprise the listener by going in another direction, to the IV chord.
   

These expectations are all on the subconscious level, of course. The listener isn't consciously aware of them, but they're real, and you can use them to help create the effects in your music that you want to achieve.

Of course, there's more to a song than chords. Your melody and lyrics play a large part in the way your song affects a listener, but creating the right supporting harmony only makes the effect that much stronger. The fact that you can do that with just these three chords goes a long way in explaining why I, IV and V may be the three most important numbers in popular music.

Using I-IV-V to Strengthen Your Melodies

Building a song on a progression with a larger number of chords (or with more complex chords) can result in a melody that is strongly influenced by the underlying chords. This isn't necessarily a bad thing, but sometimes you may want to create a more independent melody, one that doesn't rely so much on the underlying harmony to work. A good way to do this is to restrict yourself to using only the I, IV and V chords while creating your melody. The relative simpleness of the chords will force you to work a little bit harder on the melody to keep the whole thing sounding interesting.

Even advanced songwriters can use this technique to build stronger melodies, and once the melody is complete, you can go back and modify the chord progression. There are many ways to enhance a chord progression, and I'll talk about this in future posts. The I, IV and V chords work so well, however, that you may be pleasantly surprised to find that your song sounds good just as it is.