When we need to know what chords we can use in a certain key, we’re talking about diatonic chords. Diatonic refers to using the notes that a specific scale makes available to us. In western musics twelve possible notes, we reference a certain combination of steps and half steps, or tones and semi-tones, that give us the major scale. In today’s post, we’ll be looking at the C major scale to help establish this bit of knowledge. Simply because in C major, there are no sharp or flat notes!
Without any sharps or flats in the C major scale, we have the following notes;
C – D – E – F – G – A – B
When playing anything in C major, these are the notes available to you. This gives us the basis on understanding what chords can be played in this key. To start, we would build triads based on each note of the scale. Again, in C major, we would have no sharp or flat notes and therefore no sharp or flat chords.
The Pattern
There’s a couple of things to be aware of when looking at the diatonic chords in any given key. Firstly, the chords are bound to a specific formula that can help us figure out what is a major chord and a minor chord in a key. Let’s take a look at this below, using ‘M’ to represent major, and ‘m’ to represent minor. The last chord in the formula is a diminished chord;
M – m – m – M – M – m – D
I – ii – iii – IV – V – vi – vii
A more conventional way of labelling the major and minor chords in a diatonic progression, would be to number them with roman numerals. Capitals would represent the major, and lowercase the minor. Lowercase also represents the diminished seventh chord. These methods of labelling the chords diatonically in a major key gives an easy to read template to help us put together chord progressions or even transpose songs into other keys. Let’s take a look at what chords we’re given in the key of C major. Note that the diminished chord’s symbol is a small circle.
You can take this formula and apply it to any key signature and it will give you that key’s diatonic chords. For example, the key of B would be – B, C#m, D#m, E, F#, G#, A#dim. Providing you know the notes in any given key, you can quickly work out what chords fit into it diatonically.
Putting it into practice
Practically speaking, it’s all well and good knowing what chords a major key gives you, but how do you go about applying them? As a hypothetical, consider being in a setting with other like minded musicians and someone calls out to jam a one, five, four chord progression in C, a typical blues style progression. Using your knowledge of numbering the chords diatonically, you should be able to cycle through these chords as C, G and F. Even if you’d never listening to the song, armed with the diatonic chord knowledge of the key should help you instantly join in and take part in the jam.
You could also look into the chords your favourite songs use, and work backwards into figuring out what key or progression they could be using. More often than not, song in major keys will feature the I, IV, V chords in some capacity, closely forward by the minor chords available in they key to give the track some emotional depth.
Of course, there’s no hard and fast rules on having to stick to the chords a single key signature gives you. There will always be exceptions when songs dip in and out of or borrow from different keys. Knowing the diatonic chords of any key is an incredibly useful skill however, so don’t neglect it! Click here to book a lesson to help you get to grips with diatonic chord progressions.
TOP TIP – Need the diatonic chords for any minor key? Just start from the vi chord in any major key, and you’ve got the relative minor key. Click for a quick example.