Our brains and bodies respond naturally to rhythm.
This can be a biological rhythm. For example, the heartbeats of a mother and baby will synchronise with one another when they interact closely, and similar effects have been reported for couples.
But we also respond to external rhythms. The tempo of a song can naturally alter our breathing rate and heart rate.
http://www.doppel.london/ttblog/2016/3/9/how-doppel-works
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