Let’s be clear: these are only very broad trends and there are many exceptions to the rule, such as Pharrell Williams’ Happy, and Rihanna’s Diamonds, which were both huge hits with upbeat lyrics. But overall, there does seem to a shift into a darker, angrier, place.

The reasons are unclear, and Komarova is reluctant to offer any specific hypotheses. “[But] one may speculate that this is related to some changes that take place in the society.”

Shamir agrees, pointing out that in the 50s most popular music was a form of escapism – but since the 60s it has been much more socially engaged. “Music changed its role from fun expression to an expression of political views.” Perhaps this can partly explain the shift, but it has to be said that the vast majority of tracks today are not protest songs.

Mood river

If scientists are not certain about what’s driving the trends, I thought it would be worth getting the view from someone who has crafted hit songs over several decades. So, I contacted Mike Batt, the conductor, record producer, singer and songwriter who has penned many hits including Art Garfunkel’s Bright Eyes and Katie Melua’s Closest Thing to Crazy.

Batt points out that the means of consuming music have changed so dramatically – with the streaming of songs now dictating the tracks that enter the charts. These could have determined what kinds of songs become popular – if, for instance, they have meant that older adults, who may be reluctant to stream music, and who may also be less angsty, are having less of an influence on what becomes a hit.

Batt agrees that a more negative tone in today’s pop music also might reflect social changes, though – and even if the reactions to political events are not overtly expressed as protest songs, they may still influence the overall mood.

“Songs tend, either deliberately or not, to hold a mirror up to society, or are at least be affected by what is going on in the world,” he says. “The social media generation is experiencing strongly articulated stress daily. The aggression present in politics and in religious and racial tensions are no greater today than they have always been, but they are thrust more often and more directly into the faces of people. This is bound to reflect in our songs.”