Prediction error needs a source of tension to spend, and the harmonic series quietly supplies one. The dominant 7 chord contains a tritone — the most unstable interval that chord holds, and classical harmony's engine of motion — and the ear wants it resolved. It resolves the way physics suggests: by the smallest motion, each voice sliding a half step onto a note whose overtones finally agree. The leading tone is a half step below home for the same reason; it's the sharpest unshared tone begging to join the tonic's overtone family. This is why the authentic cadence feels like an arrival and not just a stop — two of the tensest tones in the system collapse into the two most consonant. Build the whole tension ladder from the physics and every 'rule' on the theory tab turns into a consequence: dominant function is stored tension, resolution is overtone agreement restored, and voice leading is just taking the shortest path down the ladder.