vega-mir: An information-theoretic Python toolkit for symbolic music, with applications to harmonic graphs and rubato spectra

TL;DR

vega-mir is an open-source Python toolkit that provides nine information-theoretic and statistical metrics for symbolic music analysis, demonstrated through case studies on harmonic graphs and rubato spectra.

Contribution

It introduces vega-mir, a comprehensive library with validated metrics for symbolic music analysis, and applies it to novel case studies not addressed in prior work.

Findings

PageRank of gravity-centre node correlates with marginal KL distance (rho=0.61).

Gould's rubato has a median dominant period of 66 beats, contrary to the low-rubato stereotype.

Four metrics are validated against analytic anchors and tested on an 8-composer dataset.

Abstract

We present vega-mir, an open-source Python library that bundles nine information-theoretic and statistical metrics for the analysis of symbolic music corpora behind a small, tested, citable API, and demonstrates two of them at corpus scale in case studies not addressed by the upstream Cygnus paper. Of the nine metrics, three (Shannon entropy, Kullback-Leibler divergence, Zipfian fits) were deployed in the companion Cygnus arXiv preprint; two (network analysis on chord-transition graphs and spectral analysis of rubato curves) are deployed in full case studies here; the four remaining (multi-dimensional Gini, chi-squared stationarity, Higuchi fractal dimension, interval distribution) are validated against analytic anchors and exercised as sanity checks on a bundled 8-composer dataset. The two case studies yield two main observations. First, on the fourteen MAESTRO composers with N >= 10 pieces, the PageRank value of the gravity-centre node correlates with the marginal Kullback-Leibler distance at rho = 0.61 (Spearman, composer-level jackknife N = 14); the categorical gravity-centre identity takes five distinct values across the corpus but is not itself correlated with marginal KL (rho = 0.13, p = 0.21). Second, on the 247-piece Bach multi-master corpus (Schiff, Gould, Richter), Gould holds the highest periodicity ratio of the three performers, not the lowest, inverting the clich\'e that low scalar rubato reads as "metronomic": Gould's rubato is small in amplitude but structured in time, with a median dominant period of 66 beats against Schiff's 102 and Richter's 104.