"In 2017, a Californian mathematician called Natalia Komarova was so shocked by the negativity of the songs her daughter listened to, she decided to investigate."

"Using the research database AcousticBrainz - which allows you to examine musical properties like tempo, key and mood - she and her colleagues at the University of California Irvine examined half a million songs released in the UK between 1985 and 2015. They found a significant downturn in the positivity of pop songs. Where 1985 saw upbeat tracks like Wham's Freedom, 2015 favoured more sombre music by Sam Smith and Adele. '"Happiness" is going down, "brightness" is going down, "sadness" is going up,; said Komarova of her results, 'and at the same time, the songs are becoming more "danceable" and more "party-like."' So it looks like, while the overall mood is becoming less happy, people seem to want to forget it all and dance." Inother words, Komorvoa had identified the rise of the 'sad banger,' a song whose instrumental sets you up for good times, only to sucker punch your heart with lyrics of Biblical sadness.... By 2017, the average tempo of a hit single in the UK was 104 beats per minute, down from a high of 124bpm in 2009. In the US, where hip-hop is more prevalent on the charts, it fell as low as 90.5 bpm.... Just three years later, the trend is in reverse...."

The average tempo of the Top 20 in 2020 is 122 beats per minute.

From "Pop music is getting faster (and happier)" (BBC).