In music, perpetuum mobile (English pronunciation /pərˌpɛtjʊəm ˈmoʊbɪleɪ/, /ˈmoʊbɪli/; literally, "perpetual motion"), moto perpetuo (Italian), mouvement perpétuel (French), movimento perpétuo (Portuguese) movimiento perpetuo (Spanish), is a term used to describe a rapidly executed and persistently maintained figuration, usually of notes of equal length. Over time it has taken on two distinct applications: first, as describing entire musical compositions or passages within them that are characterised by a continuous stream of notes, usually but not always at a rapid tempo; and second, as describing entire compositions, or extended passages within them that are meant to be played in a repetitious fashion, often an indefinite number of times.[1]
Types of perpetuum mobile composition
A well-known example as a technique is the presto finale of Frédéric Chopin's Piano Sonata No. 2: This figuration of rapid triplet quavers (eighth notes) continues for the duration of the movement.
As a distinct composition, perpetuum mobile can be defined as one in which part or most of the piece is intended to be repeated an often unspecified number of times, without the "motion" of the melody being halted when a repeat begins.
Canons are often intended to be performed in a moto perpetuo fashion, and can thus be called canon perpetuus.
In some cases the repeats of a "perpetuum mobile" piece are at a different pitch, a modulation or a chord progression occurs during the repeatable part. Some of the riddle canons of Bach's Das Musikalische Opfer are examples of this particular kind of perpetuum mobile/canon perpetuus.[citation needed]
Perpetuum mobile as a genre of separate musical compositions was at the height of its popularity by the end of the 19th century. Such pieces would often be performed as virtuoso encores, in some cases increasing the tempo along the repeats.
The finale of Beethoven's 22nd piano sonata, and large segments of the finales of his Tempest and Appassionata sonatas (although these are not very fast; the Tempest and the 22nd sonata are only marked Allegretto, and the Appassionata is marked Allegro ma non troppo)
"Fracture", a moto perpetuo piece based on the whole-tone scale composed by guitarist Robert Fripp and included on the 1974 album Starless and Bible Black
^This is most often performed with a rather insignificant obbligato accompaniment. When scored for wind instruments, it becomes a virtuoso challenge of circular breathing and double-tonguing. Béla Fleck has performed it on the banjo.
References
^Apel, Willi, ed.; Harvard Dictionary of Music, 12th ed.; Harvard University Press; Cambridge, Mass.: 1960. p. 560
