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Authentic and Plagal Cadences in Music
Cadences are a vital element in chord progressions. In this article, we'll break down what "authentic" and "plagal" means and how you can use that knowledge in your compositions.
At the end of this article, you find an original musical demonstration that shows how beautifully the Circle of Fifths can be put into action.
Cadences move step-wise through the Circle of Fifths and are a big part of the Western music culture. Authentic means that we move counter-clockwise, plagal refers to moving clockwise. As long as you don't skip any step in the Circle of Fifths, you'll create nice-sounding chord progressions.
Before we go into some actual music, let's have a look at how the tones move through the Circle of Fifths in the authentic direction, that is counter-clockwise. You see that the distance between all the tones remains the same, and that is five chromatic steps. For that reason, we call the Circle of Fifths a Root Cycle 5 (or RC5). If we want to follow the authentic way, the direction of the stacked notes is ascending.
Let's have a look at the notation. Sometimes the notes create a perfect 5th (that's seven chromatic steps), and sometimes they create a perfect 4th (that's five semi-tones) — the reason why we did this is that we wanted to keep all the tones in one octave. We want to use those tones as roots later.
But I want to shift your attention from the physical movement to the "Harmonic Weight," which is the shortest distance between two neighboring notes. In the Circle of Fifths, the shortest distance between two notes is always five chromatic steps, (not seven)!
So, in authentic cadences, the harmonic weight always goes five chromatic steps up! So, don't confuse the physical movement and the harmonic weight. They are two separate things.
Hint: Knowing the harmonic weight is essential for voice-leading in Interval Theory!
It's quite abstract if there is no chord structure above the roots, so let's add major triads on top. Please take into account that we are not using a musical key! Every root tone is a unique tonal center. This idea goes contrary to what the Diatonic system suggests, but it opens up a whole new world of opportunities, as you'll see and hear in the musical demonstration below.
The result is very musical already, but that's just the beginning. Let's add a bit of variety and make every other major triad into a minor one. This gives us even more options and inspiration to create a beautiful composition at the end of this article. At this point, our creative efforts equal zero as everything is based on technique so far, but let rephrase this so that you see the benefit.
These are rational decisions based on techniques that we teach inside the Academy.
At this stage, your job is not to make emotional decisions (yet), but to get inspired and gather material for a sketch!
Following this process is very quick. It probably will take you more time to read this article then to write out the Circle of Fifths with triads, right?
You can switch from major to minor to your liking and at any point. We just followed a simple pattern for now, and you can take this as an inspirational starting point to come up with your own designs and ideas. Just take a bit of time and get inspired by what you hear. Give yourself some options and colors to work with right now so that you save a lot of time later when we go into the process of composing.
The only difference between authentic and plagal cadences is the direction of the harmonic weight in the lower register. On the authentic side, we went up by five chromatic steps, remember? Now we want to go down by the same distance. As a result, we move clockwise through the Circle of Fifths.
Authentic and plagal connect via reflection. It might not be obvious to you, but that's the transition into Negative Harmony and a whole new world in composition. (We'll go into that in other materials).
Everything that we just did on the authentic side can be applied on the plagal side as well. See how the harmonic weight changed the direction?
It might seem trivial to you, but be sure you know the harmonic weight between two neighboring root tones. This knowledge will serve you well when it comes to extended roots, more complex structures, and even substitute voice-leading!
Remember: The RC5 ascending creates authentic cadences, and the RC5 descending creates plagal ones! Both types of movements are reflections of one and another.
You can switch freely between major and minor triads on top of your cadences. However, put your attention to the movement in the lower register. Make sure that it goes either five up or down. This alone will give you very musical results that you can instantly turn into great music.
I'm a huge fan of triads. They connect to so many musical places such as Polytonality, Negative Harmony, Equivalents, Pentatonic, and so on. Furthermore, they are easy to use and sound great! Here are the plagal cadences with alternating major and minor triads on top.
Chord Tone Substitutions
A great way how you can add even more color and variation is by bringing in substitutions. Start simple and use basic triad structures first before you start to substitute. Always build from simple to complex, not the other way around, or you'll slow down your process.
Here are the most common scale-tone substitutions for triads that you use immediately:
Those substitutions can also work nicely as passing tones and add movement to the parts. In the example below, we go through the authentic cadence (the RC5 ascending) with alternating major and minor triads and add some line movement on top. Look at the bass and the colored notes above, and you'll spot the original authentic cadence.
The secret to developing speed in the writing process lies in the order of the steps. Start simple with writing out your root tones first. Then, add the triads above and last, use the substitutions. It's best to bring in line movement later and in a dedicated step - don't mix those steps.
Now, the time has come. We want to take this exact sketch and turn it into a full-blown orchestral piece of music. Sounds good? ... let's do this!
We've reached the moment where many composers don't know how to proceed. Let me demystify the process of the orchestration for you so that the actual problem becomes smaller.
The first thing to realize is that the composition and the orchestration are connected and not two separate things. When composing, you pick registers, shape phrasings, and build smaller sections that contain 2-4 parts. These decisions open up the potential doors when we orchestrate.
I strongly believe that you could follow all steps described above easily, so, let's hear what the basic Circle of Fifths can sound like when orchestrated.
Many thanks to our Academy graduate Marc Bercovitz who developed and orchestrated the sketch in only a couple of hours! That's a perfect example of how to turn theory into action!
Marc's choice of orchestration is a powerful demonstration of the concepts that we teach at the Academy, which include ...
Sometimes, orchestration is like a puzzle. You have to commit to the first puzzle piece so that you can build around that starting point. And the truth is that there are smart starting points that lead to great results much quicker than fiddling around for hours. Again, it comes to being organized and having a process that you can follow.
Authentic and plagal cadences are a cliche but still very powerful in composition. Since everybody uses the Circle of Fifths (for good reasons), it's good advice to find something that lets your voice stand out.
Following the Circle of Fifths step by step will give you some musical material to start with. Then, bring in technique and combine this with your taste. Here's a quick summary of what we've covered so far.
Train your ears to listen for 5s in the bass part. You'll be surprised about how much music out there uses authentic and plagal cadences for the most part.
Co-founder and instructor at Music Interval Theory Academy