>Step by step

Relative versus parallel explained

1 Let’s kick things off in traditional fashion with the C major scale. Seven notes, from C to B, played on the white key soft he piano keyboard, C DE F GA B. It’s the pattern of intervals between the notes (T-T-S-T-T-T-S, where T stands for Tone and S stands for Semitone) that make it a major scale.

4 If we then harmonise both of these scales, by stacking up alternate notes from the scale onto each note, we end up with two sets of three-note chords. These ‘diatonic triads’ are what make up each key, and the diatonic sets for both keys – C major and A minor – are the same chords in the same order, but read from different points in the sequence.

2 Now let’s play the same sequence of seven notes, but starting from a different note – A – instead of C. Now we have A B C D E F G. The pattern of intervals has changed – it’s now T-S-T-T-S-T-T, which is why it sounds ‘sadder’. This is the interval pattern of a natural minor scale, so what we’ve got here is actually A natural minor.

5 This means that, just as with the two scales, the two keys are related in the same way. A minor is the relative minor of C major, and C major is the relative major of A minor. The relative key of a minor key is always major and the relative key of a major key is always minor.

3 So even though the scales of C major and A minor start from different root notes – C and A – they actually contain the same set of seven notes, and this relationship makes them relative scales. A minor is the relative minor of C major, and C major is the relative major of A minor.

6 We can use two relative keys for different sections of a song, to create a shift in mood from, say, verse to chorus. To illustrate, here’s an example of a verse section in A minor, using a i - VI - iv - VII progression that, in this key, translates to Am - F - Dm - G.

7 In the next four bars, I’ve modulated to the key of C major, using a I - IV - ii - V progression that translates to C - F - Dm - G. These chords are all diatonic to both keys, so they sound in keeping with what we’ve heard so far, but there’s been a distinct shift in tonal centre from A to C, and in mood (from minor to major).

10 This means that if we run out of chords to use in a song that’s in the key of C major, we could theoretically use or ‘borrow’ any of the diatonic chords for C minor. C major’s diatonic set consists of C, Dm, Em, F, G, Am and Bº, while C minor’s

Eb, Ab Bb. chords are Cm, Dº, Fm, Gm, and

8 Let’s return to our C major scale for a moment. If we start from C but apply the interval pattern of a natural minor scale (T-S-T-T-S-T-T), we get a C natural Eb Ab minor Bb. scale. This works out to CD FG

The C major and C natural minor scales are said to be parallel scales because they share the root note of C.

11 So how might this work in practice? This example chord progression in C major contains the chords C - F - Am - G. It works well enough using these diatonic chords, but we can make it a bit more interesting by the addition of some chords borrowed from the parallel key of C minor.

9 If we now harmonise both these scales to get our sets of diatonic triads, we can see that we end up with two different sets of chords due to the flattened notes present in the minor scale. These sets are the chords that are diatonic to, or belong to, their respective keys – the key of C major and the key of C minor.

12 In this version, I’ve altered the second half to include chords from the key of Eb, Ab Bb. C minor, namely and The whole Eb progression now follows C - F - Am - G - - Ab Ab Bb. - - The notes in the bass part have shifted to those of the parent scale of the parallel key of C minor to emphasise the change.