Ostinato
A constantly repeated melodic or rhythmic figure.
What it means
An ostinato (Italian for "obstinate") is a constantly repeated melodic, rhythmic or harmonic figure that stays the same while the other voices change. It may be short, for instance two notes, or several bars long. An ostinato in the bass is called a basso ostinato.
Musical use
The ostinato is found in all periods and cultures. In the baroque it forms the basis of passacaglia and chaconne as well as of laments such as Purcell's Dido's Lament. Maurice Ravel built his Boléro (1928) on a rhythmic ostinato of the snare drum, over which the orchestration grows ever denser. In minimal music, rock and jazz it works as a riff or loop. It creates tension and pull.
The ostinato should be distinguished from the sequence, in which a motif is repeated on another step, from the refrain, which returns in the text, and from the loop, which repeats it technically through recording.
Performance practice
When you play an ostinato, keep it even so that the other voices can shape freely above it. Practise it first alone and then listen to the interplay. Take care not to accent it when it is background.