Tempo rubato is a disregard of certain notated properties of rhythm and tempo for the sake of expressive performance. There are two basic types of rubato practices. Contrametric rubato involves a solo melody moving in subtly or equally redistributed note values (sometimes with added notes) against a steady pulse in the accompaniment. Structural or agogic rubato involves the simultaneous retardation or acceleration of tempo of the entire performing body. Theories on rubato practice from Lodovico Zacconi (1592) to Marian Sobieski and Jadwiga Sobieska (1960) are considered, as is use of rubato by composers from Giovanni da Cascia in the 14th c. to Bartok. Historic accounts of rubato in the performances by 9th-c. singers at St. Gall as well as by Mozart, Chopin, Peter Serkin, and numerous other later performers are discussed.
Rosenblum, Sandra P.
"The Uses of Rubato in Music, Eighteenth to Twentieth Centuries,"
Performance Practice Review:
1, Article 3.
Available at: http://scholarship.claremont.edu/ppr/vol7/iss1/3