Sleep music is music chosen or composed to help people wind down and fall asleep: slow tempos, soft dynamics, few sudden changes and, often, no vocals. Lo-fi sleep playlists usually slow the beat further, thin out the drums and let warm pads, gentle piano and vinyl texture fill the space.
The most thorough summary of the evidence is a 2022 Cochrane review of 13 randomised trials involving about 1,000 adults with sleep difficulties. Listening to music for 25 to 60 minutes a day was linked with better self-reported sleep quality, with moderate certainty, but evidence on falling asleep faster or sleeping longer was weaker, and objective sleep measurements showed little or no change. Participants could not be blinded to the music, which limits confidence.
Simple habits help: a sleep timer, a low volume and a speaker or comfortable headphones that will not hurt the ears. Music can be a comfort but not a cure, so persistent insomnia is a reason to see a doctor.