Harmonic Rhythm: When to Change Chords

Choosing the right chords isn't enough: you also have to decide when they change. The same progression can sound calm or restless depending on whether it changes chords every two bars or twice per bar. That rate of change is called harmonic rhythm. It's a setting as important as tempo, and yet people rarely think about it.

One progression, three speeds

Let's take the progression i VI III VII in A minor, which you know well: Am, F, C, G. First, listen to it at the most common speed in electronic music, one chord per bar.

Now let's keep the same tempo and fit the four chords into two bars, two chords per bar. The loop becomes hurried, almost restless, even though the tempo hasn't moved.

The other way around, let's make each chord last two bars. The next figure shows only the first two chords, Am and F, over four bars; the other two would follow over the next four bars. The loop becomes broad and settled, and leaves plenty of room for everything else.

None of these speeds is better than the others. A slow harmonic rhythm suits a busy melody, a vocal with a lot to say, or genres like deep house and techno, where you're after a hypnotic loop. A fast harmonic rhythm suits a simple melody, which it pushes forward. So the useful guideline is balance: when the melody moves a lot, the chords can move little, and the other way around.

Tempo matters too. At 170 BPM, a bar lasts a little under a second and a half, so one chord per bar changes very quickly; at 85 BPM, the same bar lasts nearly three seconds. That's why a drum and bass producer often lets chords last two bars, while a lo-fi producer, working much slower, can afford to change every bar, or even twice per bar.

To spot the harmonic rhythm of a track you're listening to, follow the bass: it almost always changes note when the chord changes. Count the beats between two changes, and you'll know whether the track changes chords every bar, every two bars or more often.

Speeding up before the end of the loop

The chords in a loop don't all need to last the same amount of time. A very common technique is to speed up at the end: the first chords last a bar each, and the last bar contains two. That tightening creates a push toward the start of the next loop, just like a sentence that speeds up before the period.

In this example, the last bar moves from a subdominant, Dm, to a dominant, E, which leads back to Am. You'll recognize the tension and resolution from the first lesson in this part, packed into a single bar.

Arriving a little early

Now listen to a detail that changes the groove a lot. In the next figure, the loop Am, F is played twice. The first time, F lands right on the first beat of the second bar. The second time, it arrives an eighth note early, on the last eighth note of the previous bar.

A chord that arrives early like this is called an anticipation, and producers sometimes call it a “pushed” chord. It creates a syncopation: the chord changes between two kick hits instead of landing with one, which gives a feeling of momentum. You hear it a lot in pop, R&B, house and afro. Often, the bass anticipates along with the chords, so they change together; you can also leave the bass on the first beat and listen to whether you like that offset.

Chords that play the rhythm

So far, our chords were held. A chord can also be chopped into short hits that trace a rhythm: these are the stabs you met with house. Two rhythms are then layered: the harmonic rhythm, which says when the chord changes, and the rhythm of the stabs, which says when the chord is struck. In the next figure, the chord changes only once per bar, but it's struck five times, partly on the offbeats.

Chopping chords up like this lets you keep the harmony very simple and still have a loop full of movement. Just be careful not to fill every gap: if the stabs land on every sixteenth note, there's no room left for the drums or the bass.

Letting it breathe

One last setting, maybe the hardest: silence. A chord doesn't have to last until the next one. Cutting it a beat before the change, or leaving a whole bar without chords in the middle of a loop, creates a gap that the ear notices and that makes the chords hit harder when they return. You'll find this technique in breakdowns and before a drop, where the chords are pulled out so they can come back stronger.

Listen to that silence on the fourth beat. It lets the drums through, or an answer from the melody, and the loop seems to breathe. Now try all these variations yourself.

In the next lesson, we'll see how to change key in the middle of a track, for example to give the last chorus a lift.