"In The Spell of the Sensuous, the writer David Abram describes two friends meeting again after a long time. If we should chance to overhear them, he says, we might well notice 'a tonal, melodic layer of communication beneath the explicit meaning of the words, a rippling rise and fall of the voices in a sort of musical duet, rather like two birds singing to each other.'
"Each voice mimics a portion of the other's melody, at the same time adding its own inflection, which is then echoed by the original speaker, 'the two singing bodies tuning and attuning to one another, rediscovering a common register, remembering each other." This tuning and retuning, this remembering, is what is called 'entrainment'
"It is hardly surprising that human beings should attune to one another in this way. After all, we live in a rhythmic universe, in which the earth revolves around the sun and the moon around the earth. Our bodies are rhythmic organisms, containing breath and pulse and heart beat. If you put two grandfather clocks in the same room, their pendulums with fall into unison within a couple of days. In the same way, when people talk or sing or move together, we tend to 'entrain,' or synchronize our pace with one another. This is one of the delights of good conversation: not just the stated theme, the surface content, but the underlying pleasure of entrainment, the half-conscious pas de deux with someone else's mind."
~ Christian McEwen, World Enough & Time
I've always been fascinated by rhythm and resonance, so this was a really beautiful idea to me.