Written by Gary Ewer, from “The Essential Secrets of Songwriting” website.
I truly believe that most of the time we worry too much about our chord progressions; they are the aspect that can get by with the least amount of innovation, and as long as they simply work, you’re fine. The I-IV-V-I progression has been the foundation for some of the world’s best songs. Having said that, some basic chord substitutions can go a long way to add a spark of life to a song.
To substitute a chord means that you are replacing one chord with another of a similar function. A chord’s function is a bit of an abstract concept. To help understand it, think about going for a walk: you’re either in your house (the tonic function), on your front doorstep (the dominant function) out on the sidewalk (the subdominant function), or “out there somewhere” (all the “other chords”).
Let’s look at some specific examples using the key of A major. The tonic function is, of course, normally represented by the tonic chord, A. But the tonic function can also be fulfilled to a certain degree by using other chords that share some of the same notes. For example, the vi-chord, F#m, uses the notes F#, A, and C#. Two of those notes, A and C#, are also found in the I-chord, so that makes the vi-chord in most cases a good substitute for the I-chord. The iii-chord, C#m, is also a possible substitute for a I-chord because it also shares a couple of notes: C# and E.
Using a vi-chord when you’d expect a I-chord creates a “surprise” – a deceptive cadence – if you use it at the end of a phrase, and that surprise can be refreshing. But be careful using it too much. Surprises may lose their important quality of unexpectedness if they happen all the time.
IV-chords are nicely substituted by ii-chords because they share the two of the same notes. And V-chords can be substituted with iii-chords, though you may find that substitution to be a bit less satisfying: we usually like to hear strong dominant chords, and using a iii-chord has a way of weakening the dominant function a bit too much. Think of it this way: there are many ways you can explore your neighbourhood, but there are fewer ways to enter your house.
All this can get quite wordy, so how about a couple of examples to demonstrate the power of chord substitutions.
- In this one, a basic I-IV-V-I is played four times: Sample 1: I-IV-V-I (opens in a new window). And while there is nothing inherently wrong with that, your song might benefit by balancing that standard progression with some substitutions. So the solution might be to substitute I-IV-V-I with vi-ii-V-vi for the 3rd and 4th play-through: Sample 2: I-IV-V-I replaced with vi-ii-V-vi for 3rd and 4th iterations
- In this one, you’re looking to create something unique from this standard progression: I-V-vi-iii-IV-V-I. Try this: vi-iii-I-V-ii-iii-vi: Sample 3: I-V-vi-ii-IV-V-I replaced with vi-iii-I-V-ii-ii-vi
What you need to always keep in mind to make these substitutions work is the melody note(s) at any given time. The examples given here simply show how one chord substitutes for another. How you know if it works is if the melody note at the moment fits the chord you’ve chosen.
Chord substitutions can be a novel way to add a bit of colour to your otherwise mundane progression. Always keep in mind that boring progressions are not usually a problem, but if you find that it’s a bit overworked in your song, substituting chords can be the modification your song needs to keep people interested and listening.