Pop music is too loud and melodies have become more similar, according to a study of songs from the past 50 years conducted by Spanish scientists

Pop music is too loud and it all sounds the same. That's the conclusion of scientists at the Spanish National Research Council, who have published a new report on songs released between 1955 and 2010, showing the "diversity of … note combinations … has consistently diminished in the last 50 years".

Measuring the Evolution of Contemporary Western Popular Music, by Joan Serrà, Álvaro Corral, Marián Boguñá, Martín Haro and Josep Ll Arcos, appears in the journal Scientific Reports . The researchers used a dataset of 464,411 music recordings to analyse what has changed – and what has stayed the same – over the past half-century of song. "Many of [music's] patterns and metrics have been consistently stable for [this] period," they wrote. "However, we prove important changes or trends related to the restriction of pitch transitions, the homogenisation of the timbral palette, and the growing loudness levels."

When researchers write about "pitch transitions", they mean the way notes are used – the variety of intervals, and the difference between one melody and another. Melodies are becoming more and more similar, Serra explained to Reuters. "We obtained numerical indicators that the diversity of transitions between note combinations – roughly speaking chords plus melodies – has consistently diminished in the last 50 years."

Not only are the melodies of songs more similar than they used to be, the timbral palette employed – the sounds of the instruments – has also grown narrower. A trumpet's sound, its "timbre", is very different to the sound of an electric guitar or electric piano. But now, apparently, songs are relying on a much smaller range of timbres than in the past. When so many instruments are synthesised, perhaps, or rely on digital processing, the trumpet begins to lose its trumpet-ness.

Finally, the research team found scientific evidence for the so-called "loudness war". Owing to mastering and compression techniques, new songs are literally louder than old songs. Or, as the scientists put it: "The empiric median of the loudness values x grows from −22 dBFS to −13 dBFS, with a least squares linear regression yielding a slope of 0.13 dB/year (p < 0.01, t-test)." Despite this fact, the Spanish team also found that songs' "absolute dynamic variability has been conserved" over the years. In other words, the overall dynamic range of recordings – the distance between a song's quietest and loudest moments – has remained more or less the same.