Tuning and Balance

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Tuning is a funny thing. In some respects it is a very objective element of music, clearly explicable in terms of acoustical properties. We’ve understood perfect intervals since Pythagoras after all. But when you start measuring sounds with human ears rather than scientific instruments, things become less clear-cut.

Our ears pick up the both the fundamental of a note and the halo of overtones that all sounds other than sine waves carry with them, between the frequencies of 20 Hz and 20,000 Hz. How our brains render this collection of sounds into a perception of pitch, though, is complex and not fully understood. It’s clear we perceptually wrap the overtones into the fundamental that generates them, producing a sensation of a single note of a particular quality rather than hearing lots of different related notes as would be displayed on a spectrogram. But this combined, perceptual pitch is not necessarily identical to the fundamental: the overtones can inflect our sense of tuning as well as of quality.

Hence, a lot of the problems that we experience in rehearsal in terms of tuning can actually be traced to matters of tone quality rather than aiming for incorrect pitch. Tone colour, vowel shape and balance can all affect our sense of intonation (and all these can usually be traced in turn to issues of vocal production or harmonic understanding).

I had a fascinating illustration of this recently when a friend sent me a learning track for a song her chorus was about to start. She was worried that one note in the bass part was (and I quote) ‘as flat as a witch’s tit’. (Never let it be said she has a dull turn of phrase.) She asked me to listen to the bass-predominant mix to see what I thought, adding that it sounded fine on speakers, but the problem arose when you listened to it through headphones.

So I listened through speakers. No problem. Not really expecting to hear anything different, I plugged in my headphones – and suddenly saw her point. I switched over left and right ears, and it got a bit better. This is when the penny dropped that the problem wasn’t tuning, but our perception of tuning.

The note in question was a chromatic passing note which lay on the flat 5th of a half-diminished chord. And in a cappella singing, it would want to sit a little lower in pitch than it would sound in equal temperament anyway. But in terms of balance, it would want to be sung more lightly than a root or a fifth; it would want to smoosh into the chord to add colour rather than stand out to provide structure.

When both ears were getting input from all parts, the brain could put together the gestalt of the harmony and perceive this note in context, even when the bass line was more predominant than you’d perform it. But when one ear had nothing but the bass line, and the other ear everything else, the note stuck out, sounding heavy and dull – indeed, flat. The pitch was the same each time of course, but the context of the overall sound affected whether we actually perceived it as in-tune.

People get very antsy about tuning. Tell someone they’re flat and all their confidence leaks away (which of course encourages them…to sing flat). But ask them to ‘lighten’ a note and they will intuitively adjust the balance of overtones within their sound and the volume level within the chord until it sounds right. Heck, they may even lift the pitch a little. But most things we hear as intonation issues can be sorted out without freaking people out with talk of their tuning.

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