What is Modulation?
A few months ago, an adult guitar student asked me about a concept called modulation. He was wondering if the main riff from CCR’s “Down On the Corner” modulated from C to F. I explained that no, this was not modulation but rather just a guitar riff that changed as the chord progression changed (take a minute to listen to the song if you haven’t already—it’s a classic).
My first explanation did not illustrate the concept of modulation sufficiently, so we’ve had a running joke going ever since then where, after I explain some idea or show him some song, he exclaims “Oh—so that’s modulation!” I always answered no, and after a few weeks of these antics, I decided to spend an entire lesson discussing modulation. Since then, I’ve been thinking that it is time for a posting on modulation, so here we go.
If you look up the term modulation in a dictionary you’ll see that the root word “modulate” means to change, alter, adjust, and so on. In different fields, the word can have more direct meanings, and this is certainly true in music.
There really are two definitions of modulate in music: one that means to change key, and another that means to vary the volume of sound emitted from some source. The first definition is what we most commonly deal with, so we’ll spend our time discussing it (the second definition comes in handy when talking about the physics of sound rather than music theory).
Modulation = Key Change
When we are talking about a song, modulation means to change key. This can come into play in a variety of scenarios.
First, let’s say you are playing in a band, rehearsing a Led Zeppelin song. The lead singer has to strain his or her voice to hit the high notes, so the group decides to change the key of the entire song to make things easier. This is an example of modulation—you have changed the key of the entire song. The act of changing keys is where the term modulation would fit into this scenario.
Next, modulation can happen during a song. This will typically happen in the bridge of a pop song, or in a portion of the song where intensity needs to be heightened. Generally, you don’t see modulation in modern music unless it is with the goal of adding power, momentum, or intensity to a section of music—in other words, it needs to be deliberate or we tend to not see it. A great example of this happens at the end Bon Jovi’s “Livin On a Prayer.” The chorus (or refrain) modulates up a minor third at the very end of the song to ramp up intensity right before it ends. This means that the chord progression that first started on an Em chord changed (modulated) to begin on Gm instead.
Finally, modulation commonly occurs within a movement of a symphony or, more generally, in classical compositions written in what we call binary or ternary form (there are others, too). On a micro level, each section of the piece has its own chord progression (let’s say something like I-vi-ii-V-I). These don’t tend to modulate, but the different, large sections do change key. This ends up giving us many different sections that might all be in different keys. However, the first and the last section will be in the same key in order to give the piece a complete feel. In fact, it is the modulation away and then back to the “home” or first key that can help music tell a story, with a beginning, middle and end, with the appropriate tension and release. This is quite a complicated subject, and though I am tempted to go off on a modulation tangent, I’ll leave you with that simple explanation to get the gist of modulation in classical music.
In Two Words
Put into two words, modulation in music means to “change key.” I talked about three scenarios where modulation occurs, but there are certainly more instances. Modulation is a powerful tool in music and, and a concept that all musicians should become familiar with. That’s all for now—rock on!