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In this post I suggested a model to think about harmonic charge – the degree and quality of a chord’s inherent energy. This is useful for making arrangement decisions at the primary harmony/big-picture planning stage. It can also help with concrete questions of voicing.

First, some background. The Barbershop Harmony Society’s Arrangement Manual suggests that the best spacing for close-harmony arranging is with a 10th between lowest and highest notes, as this is the optimum spacing for producing overtones. The Sweet Adelines Manual, though, makes a distinction between closed and open voicings – that is, voicings where the notes in the chord are as near as they can be to each other, versus voicings that are more spread out – and recommends that a mixture of the two makes a good effect. The BHS prescription is more concerned with sonority, that is, while the SAI approach is also concerned with musical flow.

If you look at the work of top-class arrangers such as David Wright or Renee Craig you see that, not only do they follow the SAI principle of varying the spacing of voicing (well, Renee pretty much invented women’s barbershop arranging, so no surprise there), but there is an interesting correlation between voicing, harmonic charge, and tessitura.

Whenever they leap out round the circle of 5ths – i.e. to a more active chord – they move to a closer voicing, and when they resolve back to the tonic, they’ll open the voicing up again. That is, they respond to the inherent harmonic charge of the chord by giving the singers a tighter chord to sing, which will in turn add more rattle and jangle to the sound. This will also involve a higher tessitura, especially for the bass (a) since tight voicings sound muddy if they’re too low and (b) the tenor’s role of harmonising above the lead gives relatively little room for it to move about.

Actually, the classic barbershop forward-motion swipe captures this dynamic too: moving from a major triad voiced at a 10th to the more tense 7th chord on the same root voiced at a 6th via the bass and baritone moving into a higher tessitura:

When coaching performers, I liken this arrangement device to the Bernoulli effect. I ask singers to breathe out with a wide mouth, and then again through pursed lips. They’ll notice that the air pressure is much stronger when it is passing through the smaller aperture. Likewise, I suggest, the musical pressure is higher when the gap between tenor and bass is smaller. By duetting the outer parts, you can chart the patterns of tension and release in the voicings – which, if the arranger has done their job well – will match the ebb and flow of the chords’ inherent energy.