How to Know What Key Your New Chord Progression Is In

Let’s say that you’ve been working out a new chord progression, and you’ve found something — a combination of 3 or 4 chords — that really seems to work. The trouble is: you can’t figure out what key that progression is in. How do you identify it?

The first question you might ask is this one: why do you need to know the key? If you’ve been randomly putting chords together, and you’ve finally found a set of chords that work well, you may be able to get the melody working by that same random process.

“Random” in music need not be as negative as it sounds. To say you’re putting your song together by using a random kind of process sounds a bit disorganized, but keep in mind that as the songwriter, you’re tapping into your musical imagination and sense of creativity, and so “random” isn’t truly completely random.

Still though, even if your new interesting chord progression was arrived at through some random process, you may still want the reassurance (or maybe you simply have the musical curiosity) that those chords all work in a certain key. How do you identify that key?

We know that for every major and minor key, there are a set of chords that naturally exist. You simply play a 3-note triad on the top of each scale note, and those are the chords that naturally exist.

For example, in C major, the 7 chords are: C, Dm, Em, F, G, Am, Bdim. In C minor, the 7 chords are: Cm, Ddim, Eb, Fm, Gm (or G), Ab, Bb.

So let’s use a short progression like the following as an example: C Eb F G C. How do you identify the key?

Here’s a simple 2-step process you can use:

1. Identify the key to which most or all of the chords belong. In our example, most of the chords belong to C major, with Eb being the only one that doesn’t.
2. Look at the first and final chord. (In our example, C is the first and final chord).

You’ll see that in our example, the progression is mainly in C major. The Eb chord is a so-called “non-diatonic” chord. Non-diatonic means that the chord doesn’t belong to the key.

There are many different categories of non-diatonic chords. They include secondary dominants, borrowed chords, and others. We don’t need to worry about those today. It’s enough to know that the progression resides mainly in the key of C major.

Sometimes, though, the answer isn’t so clear. There are times that you create a progression where most of it seems to sit in one key, and then takes a strange turn at the end. Example: F G F G C Bb Eb. This progression starts in C major (F G F G C) and then moves toward Eb major at the end (Bb Eb).

And other progressions just seem a bit more random: C/G  G  Db/Ab  Ab  (the note after each slash indicates the bass note). What key is it? Well, it’s hard to say, but that shouldn’t stop you from using it if you like it. You could say that it starts in C major and moves to Db major, or perhaps to Ab major. Some progressions are like that: very hard to pin down.

Let’s try that 2-step process with a few other progressions. The answer is given after each one:

1. Am G Dm G C (C major)
2. Em Dm Em Dm Am E7 Am (A minor)
3. F  Dm  Db7  C (F major or possibly C major)
4. G  B  Em  D  C  G (G major)
5. E  A  E  F  Bb  F  G  C (This one wanders a bit, from E (E A E) to Bb (F Bb F) and finally to C (F G C).

I find it more musically interesting to try to identify keys of “twisted” progressions than anything else. If you’ve been letting your musical imagination wander to the extent that you find yourself creating some interesting progressions, don’t assume that it’s somehow invalid simply because you can’t identify the key.

Those kind of “nameless” progressions can be fascinating, and can add a sense of freshness to your songs. Figure out how to pair them up with a beautiful melody, and leave the worry of key identification to some other time.

Written by Gary Ewer. Follow Gary on Twitter

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