The Null Device

Crunching the charts

Data wonks at the social music-streaming site last.fm have been taking advantage of their vast repository of recorded music to correlate analyses of the music (made using cold, hard signal-processing algorithms, not anything more subjective or fuzzy) with data from sales charts, determining how the characteristics of popular music have changed in response to cultural trends. The results make for fascinating reading.

Among findings: by looking at how percussive tracks in the charts were (i.e., how strong and regular a rhythm they had, according to spectral analyses) they pretty much pinpoint the rise of disco in the mid-1970s, a change towards more strongly rhythmic tracks which has never been reversed:

The rise in percussivity was followed by a rise in rhythmic regularity in the early 1980s, when drum machines and MIDI came into existence. Unlike the increase in percussivity, though, this was a temporary hump, which waned in the 1990s, as people got sick of drum machines, grunge/alternative did to overproduced 1980s studio-pop what punk had done to prog, and/or simple 16-step drum machines were replaced by Atari STs running Steinberg Cubase, and equipped with more humanlike quantisation algorithms. Interestingly enough, the same study found that the hump in rhythmic regularity was accompanied by a rise in tracks with a tempo of 120 beats per minute, either out of laziness or from some folk wisdom about 120bpm being the optimum tempo:
Our first thought was that songwriters in the 80s must have turned on their drum machines, loved what they heard and wrote a song to that beat - without changing the default tempo setting of 120 bpm. I would love this to be correct, but I have a hunch that it's not, especially after having found this highly interesting manual for writing a hit single written by The KLF in 1988. They say that "the different styles in modern club records are usually clustered around certain BPM’s: 120 is the classic BPM for House music and its various variants, although it is beginning to creep up", and also, "no song with a BPM over 135 will ever have a chance of getting to Number One" because "the vast majority of regular club goers will not be able to dance to it and still look cool".
Time, as the KLF said, may be eternal, but time signatures aren't; dance music (which remained strongly clustered around 120bpm at the time of acid house and the Second Summer of Love) soon started creeping upward past 130bpm, while tempos of charting music in general moved down.

last.fm's DSP algorithms also pick out the rise of punk, with its simplistic rock'n'roll arrangements and emphasis on DIY enthusiasm over polished virtuosity, and the vanquishment of prog rock, glam and other more experimental genres; this manifested itself in a steep rise in the proportion of the charts occupied by records of low harmonic and timbre complexity (i.e., both simple melodic/chord structures and unostentatious selections of instruments) between 1976 and 1979, and map the Loudness Wars of the past few decades, as the rise of the CD and a competition for sounding louder and more kick-ass than all the music that came before conspired to annihilate dynamic range:


The percentage of loud tracks has increased from 10% in 1964 (by definition) to over 40% in recent years. So music has got louder. Well, isn't that in the spirit of Rock'n'Roll? Sadly, it isn't, because the increase in loudness has led to worse sound quality. Granted, it's louder, but boy is it flat!
Finally, another cultural trend that shows up in the data is the steady decline of the Truck Driver's Gear Shift (i.e., the tendency of songs to shift their key up one or two semitones before the final chorus, for some extra heartstring-tugging oomph) from the 1950s to the present day; presumably because that shit got old. When the incidence of gear shifts is plotted by month, however, few will be surprised to find that December has 2-3 times as many as the rest of the year; after all, 'tis the season to be cheesy.

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