Rough or smooth
Tension and calm have physics underneath. Two waves whose frequencies agree lock together smoothly: consonance. Two waves that almost-but-don't agree fight, and you can hear the fight as a throbbing called beating: dissonance. Neither is good or bad. Music is the traffic between them.
From calm to rough
Six pairs, held long so your ear can settle in. Listen for the surface of each sound: glassy, shimmering, or throbbing.
Where the throb comes from
Two close frequencies drift in and out of step: together they're loud, opposed they cancel, over and over. That wah-wah-wah is the gap between the notes, made audible. The closer the near-miss, the slower and deeper the throb.
Why this matters for everything else
The dominant 7th pushes because it carries a tritone. The suspension leans because the 4th rubs against the 3rd's chair. Every 'tension' in harmony is beating and roughness, organized. Hear both resolve:
Quiz
1 / 3Beating happens when…