Popular music is a key cultural expression that has captured listeners' attention for ages. Many of the structural regularities underlying musical discourse are yet to be discovered and, accordingly, their historical evolution remains formally unknown. Here we unveil a number of patterns and metrics characterizing the generic usage of primary musical facets such as pitch, timbre, and loudness in contemporary western popular music. Many of these patterns and metrics have been consistently stable for a period of more than fifty years. However, we prove important changes or trends related to the restriction of pitch transitions, the homogenization of the timbral palette, and the growing loudness levels. This suggests that our perception of the new would be rooted on these changing characteristics. Hence, an old tune could perfectly sound novel and fashionable, provided that it consisted of common harmonic progressions, changed the instrumentation, and increased the average loudness.

This work was partially supported by Catalan Government grants 2009-SGR-164 (A.C.), 2009-SGR-1434 (J.S. and J.Ll.A.), 2009-SGR-838 (M.B.) and ICREA Academia Prize 2010 (M.B.), European Comission grant FP7-ICT-2011.1.5-287711 (M.H.), Spanish Government grants FIS2009-09508 (A.C.), FIS2010-21781-C02-02 (M.B.) and TIN2009-13692-C03-01 (J.Ll.A.), and Spanish National Research Council grant JAEDOC069/2010 (J.S.). The authors would like to thank the million song dataset team for making this massive source of data publicly available.