The heartbeat has had a strong influence on the tempo of music. Before the invention of the metronome, the tempi of music were determined from the human pulse, and the difference between a saturnine or frenetic beat in music depended on how far it departed on one side or the other from this modulator. Thus tempi which lie close to the human heartbeat have an obvious appeal for man.

Schafer, Murray R, The Soundscape- Our Sonic E…, loc. 749