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 moves 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.
Where harmony's tension comes from
The dominant 7th pushes because it carries a tritone. The suspension leans because the 4th sits a half step above the third it replaced. Every 'tension' in harmony is beating and roughness, organized. Hear both resolve:
Quiz
1 / 3Beating happens when…