Do you ever find yourself lying in bed, scrolling through Spotify, trying to find the perfect song to lull you into a peaceful slumber? A new study published in the open-access journal PLOS ONE sheds light on the characteristics of music typically associated with sleep.

Lead author Rebecca Jane Scarratt of Aarhus University in Denmark and her team analyzed 225,626 tracks from 985 playlists on Spotify labeled as “sleep music.” Using Spotify’s API, they compared the audio features of these tracks to a dataset representing music in general.

The study found that sleep music tends to be quieter, slower, more often instrumental and played on acoustic instruments compared to other types of music. That’s not at all surprising, echoing the findings of previous research, such as this 2019 study from Tokai University in Japan, which found “the characteristics of music to improve sleep quality were slow tempo, small change of rhythm, and moderate pitch variation of melody.”

However, the researchers identified six distinct subcategories of sleep music, with three of them aligning with typical characteristics and the other three subcategories being louder and more energetic. These tracks included popular songs such as “Dynamite” by BTS and “Lovely” by Billie Eilish and Khalid.

The study’s authors speculate that despite their higher energy, these popular songs could potentially aid relaxation and sleep for some people through their familiarity. However, further research is needed to explore this possibility and understand why different people choose different music for sleeping.

The findings of this study highlight that there is no “one-size-fits-all” when it comes to sleep music. It also has implications for the future development of music-based strategies to help people sleep, and for our understanding of how music is used to regulate human behavior in everyday life. So while slow ambient music can be great for relaxing before sleep, equally effective might be simply letting your favorite music play in the background, even if it might be a high-tempo, high-energy nightclub banger.

It’s worth noting that the connection between music and sleep is a topic of ongoing research. A number of studies have found that listening to music before bed can help to improve sleep quality, including reducing the amount of time it takes to fall asleep and increasing overall sleep duration.

One study published in the Journal of Advanced Nursing found that participants who listened to 45 minutes of soothing music before bed had significantly better sleep quality compared to those who didn’t listen to music or listened to an audiobook. Another study published in the Journal of Sleep Research found that listening to classical music before bed resulted in improved sleep quality, including longer sleep duration and less awake time during the night.

Actually, lots of people use music as a sort of sleeping aid. A survey by psychologists from the University of Sheffield found that listening to music close to or during bedtime helps participants sleep better because it blocks external stimuli, induces a mental state conducive to sleep, offers unique properties that stimulate sleep, or simply because it’s become a habit. Overall, 62% of the 651 respondents confirmed that they play music to help themselves sleep.

But listening to music before bed isn’t always a good idea. In fact, it can sometimes backfire horribly, causing dreaded ‘earworms’ — catchy songs that are stuck playing inside your head even hours after you listened to them. Neuroscientists at Baylor University found people who experience one or more earworms per week at night were six times more likely to report poor sleep quality compared to those who rarely experienced earworms. Subsequent brain scans showed those who caught the dastardly earworm had slow oscillations during sleep, a marker of memory reactivation. These telltale oscillations were most active over a region of the primary auditory cortex which is known to be implicated in earworm processing. In other words, the brain scans showed how the earworms were triggering memories of the song time and time again.

For some, listening to relaxing music before bedtime may indeed work as a sleep aid. Others, however, may find the experience way too stimulating and stay awake well into the middle of the night because they can’t shed the earworm.

“If you commonly pair listening to music while being in bed, then you’ll have that association where being in that context might trigger an earworm even when you’re not listening to music, such as when you’re trying to fall asleep,” said Michael Scullin, a neuroscientist at Baylor.