Lullabies are pieces of music intended to be sung or played to children. The most traditional use of lullabies is to put infants to sleep. As a result, they are traditionally simple, soothing, and repetitive. Though they can be traced to ancient times, they also found a place in western musical tradition.
The term 'berceuse' is commonly used as a denomination for art music pieces which are basically instrumental lullabies. Berceuses are usually written in 6/8, making use of simple harmonies.