Minor Keys Explained - Learn Guitar Theory Part 5

In the previous lesson what key is it in, we looked at how a key is defined by a group of chords who's notes all belong to a particular scale. Minor keys follow the same theory but there's a few things that make it a bit more complicated. There are three types of minor scale which means there are three possible minor keys, well, sort of but we'll get to that in a minute. First lets take a look at the three scales. We'll use A minor for the examples.

A Natural Minor Scale - A B C D E F G
A Natural Minor Scale Formula - 1 2 b3 4 5 b6 b7

A Harmonic Minor Scale - A B C D E F G#
A Harmonic Minor Scale Formula - 1 2 b3 4 5 b6 7

A Melodic Minor Scale - A B C D E F# G#
A Melodic Minor Scale Formula - 1 2 b3 4 5 6 7

Let's start with the easiest, A natural minor. This is the relative minor scale of C major, in other words it shares the same notes as the C major scale. Therefore, the chords in the key of A natural minor are the same chords that belong to the key of C major. The only difference is the chord order. As explained previously, the order of chords in a major key are ...

Maj - Min - Min - Maj - Maj - Min - Dim

In the key of A natural minor the chords follow this order.

Min - Dim - Maj - Min - Min - Maj - Maj

And for four note chords it would look like this.

Min7 - m7b5 - Maj7 - Min7 - Min7 - Maj7 - Dom7

The only effect this has is the chord numbers will be different. For instance, a I-IV-V in C major is C F G. In A natural minor it will be Am Dm Em. If you don't know what chord numbering is all about, don't worry, we'll cover that in the next lesson.

The chords that belong to the harmonic and melodic keys are as follows.

Harmonic Minor Chords

Min - Dim - Aug - Min - Maj - Maj - Dim
Min/Maj7 - m7b5 - Maj7#5 - Min7 - Dom7 - Maj7 - Dim7

Melodic Minor Chords

Min - Min - Aug - Maj - Maj - Dim - Dim
Min/Maj7 - Min7 - Maj7#5 - Dom7 - Dom7 - m7b5 - m7b5

Strictly speaking, you could choose any of the chords from one of those minor keys and they will all be in key. In reality however, some of them chords will sound horrible or just plain wrong when played together in sequence. This is where it can all get a bit confusing but we don't want confusion, we just want the basics so there's a few things you'll just have to take my word for otherwise the theory will start getting very in depth. To understand the reason why we have three minor scales, we have to know about tension, and then take a short history lesson.

In music, chord progressions and melodies rely on a certain amount of tension. This is usually done with unstable sounding notes that give a feeling of needing to go somewhere or resolve. We can skip the theory here but a good way to get the idea is to sing Do Re Mi Fa So La Ti Do. Now sing it again but this time when you get to 'Ti,' stop singing. You should get the feeling of it sounding unfinished, it really needs to go back to 'Do' otherwise it sounds unsettled - it needs to resolve. That's a form of tension in music.

Chord progressions follow the same principle. The strongest form of tension in a chord progression is when we go from the V chord back to the I chord. You'll be pretty familiar with the I-IV-V chord progression. In the key of C this is the chords C(I) F(IV) and G(V). Play that chord progression and listen to it. First play C F G and then finish back on C. Now do the same again but after you play the G, just stop. It feels like it wants to go back to C or it's just left 'hanging'. The tension will sound even stronger if you make the V chord a V7, or in other words, make the G a G7. Try it!

Years ago when composers started playing around with the minor key, they realised that the chord progressions had very week sounding resolutions. You can try this yourself, play a I-IV-V in a minor. The chords are Amin, Dmin, Emin.

You can hear how the Em doesn't go back to the A minor with anything like the tension that you get with a major key. The solution to this problem was to substitute the V chord for a major chord, i.e., make the chord progression Amin, Dmin, Emaj (or E7). Doing this makes the chord progression sound more stable, the only problem it would cause is that our melody lines over the new chord would have an altered note, which in this case would be the G# (the minor third in e minor). No problem, we just make the G# a G natural when the V chord is being played. If you take a look back at the notes in the harmonic scale above, you'll see how we have turned the natural minor scale into a harmonic minor scale. In effect, it's just a natural minor with a raised seventh.

When composing or improvising over this new chord progression, we can use the natural minor scale (for our melody or improvisation) over the I and IV chords, then switch to the harmonic minor for the V chord. Another option would be to stay strictly within the harmonic scale and use the new chords from produced by it.

Back in the day, composers were a lot fussier than we are today. While the new harmonic minor scale solved one problem, it also created another. It created a three semitone leap between the 6th and seventh scale degree. Not only did they think this sounded awkward but it made things difficult for some vocalists who were used to singing melody lines with smaller steps. The answer to this problem was to also raise the sixth scale degree by a half step, hence the melodic minor scale.

This all sounds a bit silly but back then it was more important to them. As you can imagine this caused all kinds of problems for composers. Some loved it some hated it.

Back to today and things are a little bit different. Musicians love sounding different and love experimenting. So much so that there really isn't any kind of uniformity to using minor keys. It's pretty much mix and match or do what you like with them. You can use one of the minor scales and chords for an entire song or you can mix any chords and notes from one to the other. This makes it harder to work out what key a song might be in.

The good news is for most popular music you find some commonalities that is mostly the V chord is altered to use the harmonic minor scale. Two very common chord progressions that do this are (in the key of A minor) the i-iV-V Am, Dm, E (or E7) and the I-VII-VI-V Am, G, F, E (or E7).

Next ... All about Chord Numbers