In the first test, the subjects said they responded similarly to two-note chords, whether they were pure, single-frequency tones, or included various combinations of overtones. If beating was really behind peoples’ judgements, the complex tones should have elicited a stronger sense of dissonance. So much for Helmholtz, it seems.
McLachlan has previously suggested that we “hear” chords in a complex, two-stage process. First, we pick out a single most salient pitch. Then, a long-term memory of the “quality” of that chord – think of the instant recognition we have of a simple major or minor chord, even if we don’t know those terms – fills in the rest. But if we hear an unfamiliar dissonant chord, we don’t have a good mental template in our memory to match it with – the brain makes a guess anyway based on the most salient pitch, but it will doubtless be wrong. This conflict between what we hear and what we “expect” to hear produces a discordant sense of unease.
If that’s so, musical training should reduce the sense of dissonance, because this supplies a wider, more varied range of common “chord templates”. That’s more or less what the researchers found, but with a curious addition. A little musical training seems to have a noticeable effect: non-musicians lose any real sense of right or wrong when on unfamiliar harmonic territory, while slightly-trained musicians develop a rigid right/wrong distinction, which relaxes with experience. As these findings lend some support to McLachlan’s learning model of dissonance, they imply that perhaps we can learn to love what jars us at first, and in a final set of experiments, the Melbourne team showed that this is so.
These findings are sure to stir up more debate about why we find some music less pleasing than others, but you can be sure it won’t be the last word. In the meantime, perhaps you should give Schoenberg another listen – or ten.