Hospitals that play music to premature babies help them grow and thrive, mounting evidence suggests.
The benefits are said to be calmer infants and parents as well as faster weight gain and shorter hospital stays.
A Canadian team reviewed nine studies and found music reduced pain and encouraged better oral feeding.
Music also appeared to have beneficial effects on physiological
measures like heart and respiratory rate, Archives of Disease
in Childhood reports.
Increasing numbers of neonatal units are using music on their wards.
Six of the studies the University of Alberta team looked at music played to babies during painful procedures such as circumcisions and heel prick tests.
One looked at the effect of music on feeding rates and the remaining two looked at the effect of music on physiology and behaviours.
Most of the trials the researchers looked at used lullabies with or without added sounds, such as heartbeats or womb noises, and one used live music - a specially composed wordless lullaby sung by a female voice and accompanied by a harp.
Other hospitals have been playing music by some of the great composers, like Mozart.
The study authors, Dr Manoj Kumar and colleagues, said: "There is preliminary evidence to suggest that music may have beneficial effects in terms of physiological parameters, behavioural states and pain reduction during painful medical procedures.
"While there is preliminary evidence for some therapeutic benefits of music for specific indications, these benefits need to be confirmed in well-designed, high quality trials."
Professor of Obstetrics Andrew Shennan, from the baby charity Tommy's, said: "Preterm births have recently increased over the past years and remain a huge problem in the UK, sometimes resulting in many long-term health problems for the child in later life, including cerebral palsy, deafness, blindness, chronic lung disease, learning and behavioural difficulties.
"The preliminary evidence that music played to preterm babies may have positive effects for behaviour and pain is very interesting and should be taken into consideration.
"Although more research is still needed in this area, the study shows that there may be simple and cost-effective ways to provide health benefits to preterm births."
Being born prematurely - before 37 weeks - is responsible for 75% of neonatal deaths in the first month of life, and the majority of intensive care admissions.
There are a number of risk factors which may lead to premature birth including maternal smoking, infections in the womb, twin or triplet pregnancies.