The overwhelming majority of Western music is harmonised in 3rds. Starting with the root, you move up two notes in the scale to find the 3rd, then do the same again to get the 5th, the 7th, and so on up to a possible 13th. That’s how harmonies between voices and instruments are created and that’s how conventional chords are formed.
But there is an alternative and that is to layer in fourths and, as I recently discovered, this is called quartal harmony. Yes, it does sound a bit weird and yes, it’s therefore primarily a tool for harmonisation in jazz, but it’s also edgy and unsettling which means it could be a useful tool for a wide range of composers given the right application.
If you harmonise the C major scale in fourths, you get these chords:
C F B E
D G C F
E A D G
F B E A
G C F B
A D G C
B E A D
If you wanted to play these chords on a guitar, you only need a few shapes played on the middle four strings:
I’ve created my own example based on quartal harmony:
In case you’re interested, I used the following virtual instruments to create this track:
Electric Piano: Vintage Keys from Native Instruments
Drums: Studio Drummer from Native Instruments
Bass: Substance from Output
Vocal samples: Exhale from Output
Strings: Action Strings from Native Instruments
Effects: Sheperd Risers from 8Dio
I’m not sure I can see myself using quartal harmonies that often but I really enjoyed the experience of trying them out. Who knows, you may find the same?