Music is a popular method for prenatal bonding. From the second trimester, a baby’s hearing is developed enough to respond to outside noise. Studies conducted show that many babies are calmed by classical music and agitated by rock or heavy metal music. It has also been revealed that babies like music with the same tempo as their mother’s heart rate (such as lullabies for example). Also, after birth, babies may recognize music they have heard in the womb. This may not be a conscious recognition, but rather an affinity to that music.