Lullabies exist in almost all cultures. This ubiquitous method of soothing babies (and most children!) tends to have repetitive words and melodies that make them easy to transmit from generation to generation. The repetition plays a large role in why baby is so soothed—the pattern that is established becomes a recognizable and predictable part of baby's world. If you are worried about your singing abilities, don't. Your baby has been able to recognize and favor your voice since birth!