Comma

stack twelve perfect fifths. the circle won’t close.

tune pure fifths around the circle — meet the gap in music itself

Twelve fifths tuned by pure 3:2 ratios overshoot the octave by a small but audible margin — the Pythagorean comma. Equal temperament, the tuning nearly every instrument uses today, closes that gap by flattening each fifth very slightly, trading pure intervals for a circle that actually closes.

Concepts: harmony, tuning.

An interactive you play with one thumb, on Wundr.