Ostinato

An ostinato is a short melodic, rhythmic or harmonic phrase repeated persistently, usually at the same pitch, while other elements of the music change around it, and it appears across many traditions from Baroque ground-bass patterns to twentieth-century minimalism and film music. Basso continuo is a specifically Baroque performance practice in which a bass instrument and a chordal instrument such as harpsichord realize a continuous, harmonically foundational bass line from figured-bass notation, with the harmony above it improvised rather than fixed. A basso continuo line can be built on a repeating ostinato pattern, but the two terms describe different things: ostinato is a repetition technique that can appear in any texture, while basso continuo is a Baroque performance and accompaniment practice.

They describe the same idea under different names: ostinato is the classical-tradition term, riff the popular-music one.

The two describe close to the same idea, a phrase that repeats persistently in one musical voice, but the vocabulary splits by tradition. In classical and concert music the repeating phrase is called an ostinato, from the Italian for stubborn (the same root as the English word obstinate). In popular music the equivalent repeating figure is usually called a riff, a term that leans toward rhythmic or melodic brevity. Ostinato is the broader term, applied across genres and centuries, from Purcell's descending ground bass under Dido's Lament and Ravel's Bolero to the repeating figures of rock songs such as The Who's Baba O'Riley.