Finding the chords that could be used to harmonize your song is an easy process: you choose a key based on your melody’s range, write the scale for that key, and build a triad on each note. That gives you seven chords as a starting point. Before you start adding “altered” chords to your palette of sounds, check first to see if you’re getting the most out of those seven chords.
If you decide to add others – for example, a G chord while being in the key of A major – you’ve just added an “altered chord”. Altered chords require the use of a sharp or flat that doesn’t normally exist in your chosen key.
But I feel that many songwriters move too eagerly into the world of altered chords without first making the best use of the diatonic ones at their disposal.
One way of making good use of diatonic chords is to organize them into two groups – one with major chords, the other with minor. If your song is in A major, here’s what those two groups would look like:
A D E
Bm C#m F#m
(That leaves a seventh chord, G#dim, as the one left-over, and that chord can be used, if you’d like, as a substitute for E. Let’s ignore that one for now.)
By organizing the six chords in this way, you can control the overall harmonic feel of your song. The easiest way to use this method of organization is to consider using mainly minor key progressions for the verse, and major ones for the chorus.
That might give you something like this:
Verse: F#m Bm F#m Bm C#m F#m C#m F#m
Chorus: A D A D E A E A
What’s interesting about this is that the bass line implied by those chords shows similar shape between verse and chorus: a movement of up a 4th, down a 4th, etc. That similarity makes a very useful connection between verse and chorus, acting almost like a melodic motif that works like glue.
So before trying to add altered chords to your progressions, give this kind of major/minor balancing a try. It has the benefit of making the most of all the diatonic chords at your disposal, solidly locking your song into a key while giving you a great variety of harmonic sounds.
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