What makes music sound good, asks associate professor of music Dmitri Tymoczko. Tymoczko has developed a program called ChordGeometries, which represents chords and voice leadings in a variety of 3D geometrical spaces. Here are two video clips that demonstrate the program.
The first shows an excerpt from a Chopin prelude as it travels through a slice of the four-dimensional space containing seventh chords.
Source: Dmitri Tymoczko. For more information, see Tymoczko's page on the Princeton music department's website: http://music.princeton.edu/~dmitri/