# Pithoprakta

Pithoprakta (1956) is a piece by Iannis Xenakis for 46 string instruments, two trombones, xylophone, and woodblock. Premiered by conductor Hermann Scherchen in Munich on March 1957, the piece was made into a ballet by George Balanchine, Metastaseis and Pithoprakta, along with the earlier Metastaseis.

The title translates as "actions through probability",[1] and the piece is based on the statistical mechanics of gases,[2] Gauss's law,[3] or Brownian motion.[4] Each instrument is conceived as a molecule obeying the Maxwell–Boltzmann distribution law,[5] with Gaussian distribution of temperature fluctuation.[3]

Brownian motion is a four-dimensional phenomenon (three-dimensions and time), and Xenakis created the score by first creating a two-dimensional graph, necessitating some simplifications.[4] The abscissa (x) represents time at 5 cm = 26 MM, while the ordinates (y) represent pitch at 1 semitone = .25 cm.[3] When transcribed into musical notation 5 cm = one measure.[4] This length is subdivided into three, four, and five equal parts, allowing for fine differences in duration,[3] but also creating a steady pulse in each instrument part, reducing the rhythm of the random walk to steady footsteps ("a situation impossible in [the] reality [of the model]").[4] Each part gets nowhere,[4] but as a whole the mass's pitch is freely modulated and its speed determined "temperature" varies.[3]

## Sources

1. ^ Harley, James (2004). Xenakis: His Life in Music, p.13. Routledge. ISBN 0-415-97145-4.
2. ^ Ilias Chrissochoidis, Stavros Houliaras, and Christos Mitsakis, "Set theory in Xenakis' EONTA", in International Symposium Iannis Xenakis, ed. Anastasia Georgaki and Makis Solomos (Athens: The National and Kapodistrian University, 2005), 241–249.
3. Xenakis, Iannis (1992). Formalized Music: Thought and Mathematics in Composition, p.15. ISBN 9781576470794.
4. Emmerson, Simon (2007). Living Electronic Music, p.48. ISBN 9780754655480.
5. ^ Randel, Don Michael (1996). The Harvard Biographical Dictionary of Music, p.999. ISBN 9780674372993.