in music, short melodic phrase repeated throughout a composition, sometimes slightly varied or transposed to a different pitch. A rhythmic ostinato is a short, constantly repeated rhythmic pattern. Ostinatos appear in Western composition from the 13th century onward, as in the motet Emendemus in melius (Let Us Change for the Better) by Cristóbal de Morales (c. 1500–53) and in the Concerto, Opus 38 (first performed 1925), of Paul Hindemith. Use of an ostinato was particularly common in 16th-century dance pieces, notably in the bass line, where it is called a basso ostinato, or ground bass (q.v.). A single-pitch ostinato governs the “Scarbo” movement in Maurice Ravel's piano work Gaspard de la nuit (1908).