  We study the Neo-Riemannian principle of parsimonious voice-leading using
tools and techniques from classical graph theory and the modern field of
complex networks. We quantify the relative importance of particular chords
within this framework. The graph-theoretic notion of eccentricity suggests that
when working in a harmonic scheme dictated by any common musical scale, no
triad is any more isolated than any other. Complex network theory refines this
idea, and in this context provides measures of how important particular triads
might be for the flow of chord progressions through the harmonic network. We
review and compare several different such measures of centrality and
communicability.
