In 1985, the best-selling song in the UK was Jennifer Rush's The Power of Love. Thirty years on, it was Uptown Funk, by Mark Ronson, featuring Bruno Mars. From soft-rock power ballad to dance track, these were very different.
It's obviously difficult to take a sample of two songs and draw sensible conclusions about changes in popular music. But what about a sample of 500,000 songs? That's what scientists at the University of California Irvine have done, to track trends in the success of different kinds of song between 1985 and 2015.
The researchers made use of the burgeoning availability of large datasets, in this case the crowd-sourced online music encyclopedias Musicbrainz and Acousticbrainz. They analysed half a million songs released in the UK in that 30-year period and correlated chart success with the songs' acoustic features.
These were broken down into variables such as tonality, mood, danceability, and genres. The findings suggest there is a broad trend for fewer happy songs and more sad songs, while there has been an increase in the number of danceable songs. Yet while this kind of "big data" study can reveal insights about what we listen to, it's also important to look at how we listen.
Categorising songs as "happy" or "sad" depends greatly on social context and interaction. Take the example of one that topped the charts twice, 16 years apart, Queen's Bohemian Rhapsody. It's a complex production, not straightforwardly danceable, and sung from a murderer's perspective. Yet it's the source of much joyful group participation.