While brain synchrony during a duet seems like a given, it's a mystery how it happens, says Lindenberger, a psychologist. 'One could speculate that this may be related to mirror neurons, the capacity of primates and humans to imagine the action of the other person while performing actions yourself,' he says. 'The mirror neuron system could be active during synchronized guitar playing.'Lindenberger says that inter-brain synchrony may also help explain humans' ability to engage in a host of other activities and behaviors that involve couples or teams, such as dancing, boxing, tennis and mother-child bonding. 'People have an extraordinary capacity to synchronize their actions,' he says. 'When two people concentrate on the same thing, gestures and head movements are highly coordinated and supported by brain synchronicity. We think what we are getting through music has wider implications and social bonding behaviors are part of those wider implications.'"
A further implication: the sum energy of adding waves increases as the square of the number of sources when the sources are in phase, which is to say when they are synchronized, yes, but also when those sources are proximally co-located, say, for example, on a small live stage. This seems a very strong case against any equivalence of sound and the subjective qualia of music, a myth that lead us to multitrack recording and replacing live musicians with pre-recorded sound as if they were the same; the broadcast psychic energy-wave of the canned and asynchronous performances simply could not gain anywhere near the same intensity as the living sound.