A lullaby is a gentle, soothing song sung to help a baby or young child fall asleep. Parents and caregivers have sung lullabies for thousands of years, using soft melodies and repetitive words to calm restless children at bedtime. Songs like “Rock-a-bye Baby” and “Twinkle, Twinkle, Little Star” are classic lullabies you've probably heard.

Lullabies usually have simple, peaceful melodies that repeat, almost like a musical hug. The rhythm often matches a rocking motion or a heartbeat, which helps explain why they work so well.

Lullabies exist in every culture around the world, though they sound quite different from place to place. A traditional Irish lullaby sounds nothing like a Japanese one, but they share the same purpose: using the power of music to bring comfort and sleep. You might still find lullabies soothing to listen to even now, since their calm melodies can help anyone relax after a busy day.