I mentioned in my post about last week's Arrangers’ Workshop that we’d talked about the relationship between the circle of fifths and the sense of a song’s form, and that it probably needed a post in its own right to cover. So, here is that post.
I’ve written before about Harmonic Charge as a measure of the inherent energy a chord has within the context of a particular key. Here, we’re just talking about dimension of harmonic charge that involves the potential energy of distance round the circle of fifths. The other dimensions (major/minor and presence/absence of a tritone) seem to me more about flavour than structure – important considerations for a song’s expressive feel, but perhaps secondary when thinking about mapping out its shape.
So, the point about the circle of fifths is that it is measure of tonal distance. Chord III is further away from ‘home’ than chord V (as it is V of VI, which is V of II, which is V of V, and then you’re nearly home). So, chords further out round the circle inherently feel more active, as you’re going to have travel further harmonically to get back home to where the music feels at rest.