A cadence is musical punctuation. Just as a period, comma, or exclamation mark shape our reading, different cadence types create different shades of “closure.”
Main types: authentic (V–I) — the strongest, like a period at a sentence's end; plagal (IV–I) — softer, the “Amen,” often ending prayers; deceptive (V–VI) — a surprise turn, a comma instead of a period; half (I–V) — a pause mid-thought. In Classical concertos, the solo cadenza is the soloist's virtuoso improvisation before the final chord.
A cadence's strength depends on the beat and the inversion of the closing chord: a perfect authentic cadence (both chords in root position, the tonic in the melody) sounds final, like a full stop, while an imperfect one leaves a sense of moving on. Hearing cadences is the key to grasping form: it is by them that the ear unconsciously divides the musical flow into sentences and periods.
