Perpetuum mobile

Perpetuum mobile (Latin) and moto perpetuo (Italian) are terms applied to pieces of music, or parts of pieces, characterised by a continuous steady stream of notes, usually at a rapid tempo.

A well-known expample is the finale of Frederic Chopin's ''Piano Sonata No. 2:

This figuration of rapid triplet quavers continues for the duration of the movement.

Other examples include the second of Franz Schubert's Impromptus, D. 899, the finale of Carl Maria von Weber's Piano Sonata No. 1 and the finale of Béla Bartók's Concerto for Orchestra. Pieces explicitly given the title "perpetuum mobile" by their composer include Felix Mendelssohn's Perpetuum mobile, opus 119, for piano, Johann Strauss II's Perpetuum Mobile: musikalischer Scherz for orchestra and Arvo Pärt's orchestral Perpetuum mobile (1963).

The term literally means perpetual motion, and as well as its musical usage, is sometimes employed in reference to perpetual motion machines.