Academia.eduAcademia.edu

Outline

Old and New Isometries between Pc sets in the Planet-4D Model

2015, Music Theory Online

https://doi.org/10.30535/MTO.21.3.1

Abstract

The Planet-4D model introduced by Baroin 2011b is a richer model of pitch-class relationships than the standard cyclic model of the clock-face diagram: instead of the distribution of twelve points on a circle in a 2D plane, the Planet-4D model places the twelve pcs on a 4D hypersphere. Beyond the usual T/I group of symmetries, which is still featured in this new musical space, the additional dimensions yield other isometries (most notably now including the M5/M7 operations), which appear here in animated visualizations of musical pieces. The present article elucidates how these isometries are in fact well-known symmetries that do not preserve shape in most previous models with fewer dimensions. The hyper-spherical environment grants each symbol an equivalent physical position, and therefore allows for more symmetries than any 3D model. This article also shows that the model provides a visually intuitive geometric setting of pcs, in accordance with our perception of 3D Euclidean spac...

References (13)

  1. Major or minor triads provide a helpful demonstration of this larger group: the original T/I group acts simply transitively on these 24 triads; in other words, there is exactly one way to transform one given triad into another one by way of a T/I transformation. This is one of the most famous generalized interval systems as defined in Lewin 1987.
  2. Applying any of the new isometries, however, turns these triads into the so-called major-minor trichords, i.e., transpositions of 014 or 034, set class 3-3 in Forte's classification. (In Fiore, Noll, and Satyendra 2013 these chords are called "jets" and "sharks" respectively, in honor of their use in the score of Bernstein's West Side Story.) One example of such a transformation was given above in [21.3]. To give another example, the transformation turns the pitches of the C-major triad, C = (0, 0), E = (1, 0), and G = (1, 1), into the "jet" chord B = (2, 3), C = (0, 0), and E = (0,3) respectively; see Video 10 for a representation that shows [0,4,7] transformed into [11,0,3]. Of course the tonal quality of the triad is destroyed, as is the intervallic content in -see, for example, what becomes of the aforementioned sequence of triads in Beethoven's Ninth Symphony when this transformation is applied in Video 11.
  3. Some useful features of the new group are given in Proposition 2. Theorem 2, below, explains why they may look familiar to many readers.
  4. Baixas, Guillaume. 2012. "Etude des isométries du Model-Planet, un modèle de représentation des notes de musique." Master's thesis, Montpellier 2 University.
  5. Baroin, Gilles. 2011a. "The Planet-4D Model: An Original Hypersymmetric Music Space Based on Graph Theory." In MCM 2011: Proceedings of the 3rd International Conference on Mathematics and Computation in Music, 326-29. Springer.
  6. -----. 2011b. "Applications de la théorie des graphes des objets musicaux. Modélisations, visualisations en hyperespace." PhD diss., University of Toulouse le Mirail.
  7. Cohn, Richard. 1991. "Properties and Generability of Transpositionally Invariant Sets." Journal of Music Theory 35 (1-2): 1-32.
  8. -----. 2012. Audacious Euphony: Chromatic Harmony and the Triad's Second Nature. Oxford University Press.
  9. Fiore, Thomas, Thomas Noll and Ramon Satyendra. 2013. "Morphisms of Generalized Interval Systems and PR-groups." Journal of Mathematics and Music 7 (1): 3-27.
  10. Lewin, David. 1987. Generalized Musical Intervals and Transformations. Yale University Press.
  11. Mazzola, Guerino and Moreno Andreatta. 2007. "Diagrams, Gestures and Formulae in Music." Journal of Mathematics and Music 1 (1): 23-46.
  12. Mazzola, Guerino. 2002. The Topos of Music. Birkhäuser.
  13. Peck, Robert, 2011. "Nth Roots of Pitch-Class Inversion." MCM 2011: Proceedings of the 3rd International Conference on