Last issue, we looked in considerable depth at the infamous “Four Chords Of The Apocalypse” - the omnipresent sequence that has become the 12-bar blues of the modern age, such is it’s ubiquity. If you missed it, be sure to go and check that lesson out - I’m going to assume you have from here on. Ok? Awesome.
Last time, our mission was to explore how far we could “bend the rules” of this progression - this time, we’re going to break a few. Thinking back, the most important lesson from last time was the to the the “stable-unstable” principle that makes this progression tick, where we alternate stable-sounding chords against unstable ones to create a sense of movement. Now, it’s going to be difficult to make the stable chords (I and vi) any more stable than they already are, but the unstable ones (V and IV) are just begging to be messed with. This is where we start introducing “non diatonic” chords as substitutions for those unstable chords. These can be quite literally any chord that features one or more notes not found in the key of the song (in C, that’s any chord with a sharp or fl at note), but we’re going to look at some of the most common ones.
First though, some principles. The more “outside” notes your substitute chord contains, the more “out” it’s going to sound. If there’s only one non-diatonic note in there, it’ll sound pretty at home, but if they’re all out it’s going to sound more pretty jarring. Introducing notes that are sharp (relative to the key) will brighten the progression, increasing the perceived energy (as we’ll see with E7). Likewise, introducing notes that are flat (relative to the key) will darken the progression, reducing the perceived energy (see Fm). This is not a bad thing. Ok, some practical examples. Let’s begin with substituting the V chord (working in our key of C, that’s a G) with an E7. That gives us a progression that reads: C (I) - E7 (III7) - Am (vi) - F (IV) The E7 chord features a spicy-sounding G# note that’s not found in the home key, and it creates an urgent brightness that pulls incredibly strongly towards the Am that follows it.
The Am variation of this progression is particularly strong, and reads: Am - F - C - Em Let’s look at another: A very common substitution for the IV chord (F, in our case) is a iv (aka “four minor” - Fm in our case. That would give us: C (I) - G (V) - Am (vi) - Fm (iv) The “outside” note here is an A flat, which darkens the progression with a beautiful melancholic quality. You may have noticed that this note is enharmonically equivalent to the G# from the previous example (i.e. it’s the same pitch), but it has the effect of either darkening or brightening our progression depending upon the chord it’s set in. Further proof, as if we needed it, that it’s context that matters when discussing harmony. Incidentally, if you wanted to extend this chord, I’d advise using an Fm6 (F Ab C D) rather than an Fm7 (F Ab C Eb). This is because the former only has one “outside” note, while the latter has two, which might be a little jarring. Incidentally, Fm6 contains all the same notes as Dm7b5, which is another cool-sounding substitution that has a similar sonic effect.
Obviously, we can’t cover every substitution out there in this article, but I’d like to look at one more. In this instance, we’re going to deviate somewhat from the “Four Chords” progression to explore the idea of stability an instability a bit deeper. The progression will be as follows: C (I) - D7 (II7) - F (IV) - C The D7 (D F# A C) features a single outside note, and feels suitably unstable. “But hang on”, you might be saying “that progression goes stable, unstable, unstable, stable”. Yes, it does, and that should undermine the propulsion that we’re trying so hard to maintain. But it doesn’t. The reason it works is because the D7 is MORE unstable than the F, which gives us: C (stable) - D7 (very unstable) - F (quite unstable) - C (stable) The point here is that stability/instability is not an on-off switch, but rather there are many layers of stable and unstable that, when manipulated carefully, will give you an unbelievable amount of control over the energy levels of your music.
With that, I’d like to encourage you to go out and experiment; write lots of songs, and re-visit existing ones. See what you can come up with. It might be that the “Four Chords” progression is absolutely perfect for your song, and that’s ok. But if you need some more spice, now you know where to look for it.