Perpetuum mobile
In music, perpetuum mobile (English pronunciation /pərˌpɛtjʊəm ˈmoʊbɪleɪ/, /ˈmoʊbɪli/; literally, "perpetual motion"), moto perpetuo (Italian), mouvement perpétuel (French), movimento perpétuo (Portuguese) movimiento perpetuo (Spanish), carries two distinct meanings: 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 also 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. Types of "perpetuum mobile" composition. 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 are examples of this particular kind of "perpetuum mobile"/"canon perpetuus". "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. Examples. "Perpetuum mobile" pieces of both kinds include: