Today we’re going to break down how to write a chord progression when you already have a melody, also known as harmonization. You’ll see that writing chords is like solving a puzzle, and piecing together the perfect solution is both fun and extremely rewarding!
In the spirit of the holidays, we’re going to use as an example the first verse of “O Holy Night” in G Major, where we’ve removed the chords. Click play on the figure below to hear our starting point:
We’ll write chords for this melody in 3 different levels of increasing complexity, with each level following the basic rules for chord progressions that we teach at Hooktheory:
- Start your progression on the I chord (the home chord of the key).*
- End your progression with a cadence chord (in major keys, either IV or V) to link back to the I.
- Pay careful attention to which notes are stable (in the chord) or unstable (not in the chord).
* If you’re new to thinking about chords and notes in relative notation (I, IV, V for G major, C major, D major), or just need a refresher, here’s a quick plug for our book series on music theory for songwriting.
Level 1: Let’s start out simple.
Following the first rule, we’ll start our progression with the I chord. The I chord is a good choice here because it contains the notes 1, 3, and 5, and our melody in the first measure has only 3s and 5s.
When all of the notes in a melody are also contained in the underlying chord, we say that the melody is “stable” over this chord. We don’t always need our melody to be stable (and sometimes it’s impossible), but choosing a stable melody-chord combo makes your song feel musically solid, so it’s a good idea to use it as a starting point.
Our second measure contains just 5s in the melody, so we can just keep the I chord going. Sometimes the simplest solution is the best, and you shouldn’t feel like you need to change chords every measure if you don’t want to. Listen to how the I chords in measures 1 and 2 support the melody:
In the third measure we have some new notes, 6 and 4, both of which are not in the I chord. In the figure below we’ve included a little cheat sheet for you to see which chords contain which notes. Here we see that 6 and 4 (purple and green notes) are stable over both ii and IV.
Both of these chords would work, but let’s choose IV. Looking ahead, the long note 1 in the following measure suggests we could go back to a I chord, and by choosing IV now we can create a cadence.
A cadence is a fancy word for short sequence of (usually two) chords where the first chord has a strong musical pull to the second chord, giving a sense of resolution. The two most important cadences in popular music are IV → I and V → I, and here is a great opportunity to use the former one. Listen to how this cadence in measures 3 and 4 provides a sense of resolution:
Moving along, we see that measures 5 and 6 are also very compatible with the I, and for sake of simplicity let’s use it. There is something to be said about the symmetry here: since the first four measures had two measures of I followed by a cadence, we can continue this pattern by again using two measures of I, and then ending with a cadence (recall rule 2 advises us to end our progression with a cadence anyway). Creating patterns like this is important in songwriting as is helps your listeners anticipate how the song will progress.
Looking at measure 7, it seems that we won’t be able to reuse the IV → I cadence, since the of the three notes in the measure, 5, 4, and 2, only 4 is stable in IV.
Instead, let’s consider trying to use V → I. From our chart above, we see that indeed, 5 and 2 are already stable in V! But what about 4? Recall above that we mentioned that melodies don’t always have to be stable, so let’s talk a little bit about what happens when they’re not.
When a note is unstable in a chord, it creates a tension. Tension is not necessarily a bad thing, and we can actually use it to our advantage in our songwriting by exploiting the fact that our ears like having tension resolved.
In our example, the 4 only begins creating tension at the middle of the measure, and it is quickly resolved by both the 2 over the V chord and the 1 over the I chord. So in this example, the tension built up arguably makes our cadence even stronger! (Aside: it turns out that 4 is a special note specifically over the V chord which is well-known in music theory to strengthen this cadence)
And now we’re finished with our first chord progression (which turns out to be very similar to the original song chords). Let’s arrange it with some Christmas-y instrumentation to see how it sounds. Pay attention to the two cadences we wrote and feel how they pull back to the I, and in particular, how the tension we create in measure 7 resolves in measure 8.
Level 2: Expanding our palette
In this level, we’re going to branch out beyond just the I, IV, and V chords, but we’ll still follow all the same rules. In particular, we’ll keep the I chord in measure 1 to start our progression to comply with rule 1.
In measure 2, we’ve established in our last example that the I is a good fit with the 5s in the melody, but what other chords are stable under the 5s?
Referring back to our chord chart, we see that both iii and V fit the bill. V would work fine here, but we know that V is a cadence chord and wants to go back to I. But we’re just getting started, so it’s a little too early for this cadence, so let’s try iii instead!
iii is a special chord among the seven basic chords. Besides being a minor chord, it is less common than the other basic minor chords vi and ii, and so using it early in a progression makes a statement that you intend to do something interesting with your chords. iii is also special in that it has strong tendencies to two chords in particular: IV and vi.*
* For more interesting statistics on chord tendencies, see Hooktheory Trends
In a way, this makes our job for measure 3 more simple; let’s see which chord between IV and vi makes more sense! Let’s again consult our chord chart above (are you getting the hang of this?) which tells us that the 4s and 6s in the melody will naturally be much more stable over the IV than the vi, so let’s choose IV.
Note that this choice of IV in measure 3 is the same as we chose in our first progression. Back then we chose I for measure 4, arguing that the IV → I cadence gives the listener a sense of resolution. This time let’s subvert this expectation by going to a vi instead. In music this is called a deceptive cadence, because we’ve setup the expectation to go back to I, and instead went a completely different direction. Listen below and see if your ears tell you you’re about to hear a I chord, and then are surprised when they hear the vi instead:
Moving along to measure 5, we’d love to go back to the I chord due to both the 5s and 3s in the melody, and to give the progression some resolution that we intentionally withheld in the last measure. The problem is that it feels a little off to go there from the vi, which is not a cadence chord. So far we’ve been using exclusively 4-beat chords, but splitting this measure into two 2-beat chords allows us to solve this hiccup: for the first two beats we use a V chord, and the second two beats we use a I chord. The V chord works on the first two beats because of the 5s in the melody, and serves as a bridge between the vi and the I chords since it acts as a mini cadence.
For measure 6, you might think that the 1s and 3s in the melody point toward a I chord. This would normally be true, but by increasing the tempo of our chord changes in the previous measure, we’ve given our progression some momentum, and having another I chord would stall this out a bit. We could choose vi (both 1 and 3 would be stable), but let’s see what happens if we choose IV instead. The 1 is stable over IV, but the 3 is not; this will create tension on the 3rd beat of the measure which is then released when the melody moves to the stable 4.
Recall that this pattern of stable-unstable-stable is the identical to the one we created in measure 7 with a V chord. This means that by reusing the V and I from last time to end the progression, we can establish a cyclical tension and release through measures 6 and 7, which serves to enhance this final cadence to I.
Since this progression overall is a little more edgy than the last, let’s arrange it with some guitars and drums to create a pop ballad feel:
Level 3: Soft and subtle
In this final level, we’ll keep the same basic seven chords that we’ve been using, but we’re going to increase the complexity of our chord progression by adding an additional rule to our three at the start of this article:
- Treat your bass line as a melody.
When we listen to music, our ears tend to pick out the extremes: the highest notes (often the sung melody), and the lowest notes (the bass line). Treating your bass line as a melody means connecting the bass notes together so that they move up and down with intention, rather than bouncing around randomly as they often do if we don’t think too much about them.
To do this effectively we need a new tool: inversions*. An inverted chord is one where the notes are rearranged so that the lowest note of the chord is one of the other two notes in the chord other than its root (e.g. G/B is a G chord in 1st inversion, and a G/D is a G chord in 2nd inversion). Inversions are helpful for our final rule because when you invert a chord, the stable scale degrees stay the same but the bass note changes.
*For more information on inversions, see chapter 5 of the Hooktheory book 1.
By now you should be able to work out why the progression: I → V → IV → I is a good fit for measures 1-4. But here the bass line is bouncing around a lot. Let’s add a double bass playing the bass line so that you can hear this more clearly:
Now let’s listen to these same four measures, but let’s use inversions to connect the bass line:
Here the “6” superscript denotes 1st inversion, and the “64” denotes 2nd inversion (notation from classical music). So what’s going on here? Don’t worry, it’s simpler than it looks!
The V chord in measure 2 normally has the notes: 5, 7, and 2, with 5 on the bass. Since it’s in 1st inversion, we cycle once and the 7 is on the bottom.
The IV chord in measure 3 normally has the notes: 4, 6, and 1, with 4 on the bass. Since it’s in 1st inversion, we cycle once and the 6 is on the bottom.
The I chord in measure 4 normally has the notes: 1, 3, and 5, with 1 on the bass. Since it’s in 2nd inversion, we cycle twice and the 5 is on the bottom.
What we’ve accomplished is that we’ve changed the relatively bouncy bass line 1 → 5 → 4 → 1 into a much more musical one: 1 → 7 → 6 → 5. To help visualize this, the colors of the chords in the diagrams match the color of the note in its bass.
Moving on to measure 5, we would love to use a IV chord here to continue our nicely descending bass line, but this would create big problems with our melody, since none of its notes (5, 3, and 2) are stable in IV. To work this out, let’s again split this measure, choosing IV for the first half and I⁶ for the second half. The IV will create tension with the unstable 5 in the melody but this tension is immediately resolved by the stable 3 over the I⁶ chord. Here we’re choosing I⁶ instead of I so that the bass continues descending stepwise (1 → 7 → 6 → 5→ 4 → 3).
By now we’re pretty invested in this connected descending bass line, so it would be great in measure 6 to choose a chord with a 2 in the bass (then we could finish up our progression in measures 7 and 8 with a final cadence V → I and be done!). Using a ii chord here would be convenient, but again we are stuck with the problem of several unstable notes (1 and 3). To get around this we’ll make a small modification to our ii chord: we’ll make it a seventh chord. ii⁷ is like ii, but it has one additional stable note (2, 4, 6, and 1). This small change makes it so the 1 is now compatible, which reduces the amount of tension in the measure.
The final modification we’ll make is to the V chord in our cadence. This chord is perfectly fine as it is, but some might consider the note 4 a little too harsh for the feel we’ve achieved so far. A simple trick that is extremely useful when you find yourself in this position (which happens fairly frequently) is to substitute your V chord with a V¹¹. We won’t talk at length about this chord here, but for our purposes today know that V¹¹ is compatible with notes: 5, 2, 4, 6, and 1 (notably not 7 though!), and serves to “soften” the cadence to I. In general it’s an excellent substitution to try when you’re going for a more subtle cadence at the end of your progression, and as such, is a common character in many love songs and ballads from the 90s.
Let’s arrange our final progression with some light strings:
Which progression do you like the best? Let us know in the comments.
Want to write music using the notation in this article? Get started with Hookpad today and happy songwriting!