Easy Guide to Harmonising a Melody – 1 – which chords?

Let’s take it that you know the triads of the major scale, and your cadences: 

Which chords to use? 

The most important chords for us are: 

• I = Tonic 

• IV = Subdominant 

• V = Dominant 

• and we can save vi = Relative Minor for emergencies. 

It’s these chords that we used for the four most common Cadences: 

• Perfect = V (Dominant) to I (Tonic) 

• Imperfect = I (Tonic) to V (Dominant) 

• Plagal = IV (Subdominant) to I (Tonic) 

• Interrupted = V (Dominant) to vi (Relative Minor) 

Why are some Roman numerals for chords in capital and some lowercase? Capital = a major triad, lowercase = minor triad. 

Let’s take something really simple, like Twinkle Twinkle Little Star, and see if we can harmonise it with the chords above. Here’s the original melody: 

(and if you’re thinking “OH NO it’s so BORING!”, our job here is going to be to make it interesting)  

And now just using chords I (Tonic), IV (Subdominant), and V (Dominant) using minims: 

How have we done this? 

1. Take the note in the melody (i.e. C)

2. Then match it to one of the three triads to see if it fits – C fits in chords I (Tonic = CEG) and IV (Subdominant = FAC) 

3. Choose the one that sounds/fits best 

This is perfectly fine, but yes it is a bit boring, so stay tuned for Part 2…