Even the Beatles would have had trouble recognizing their peppy song in the lullaby that Andrea Zalkin sang to the tiny, fragile baby clutched to her chest in the neonatal unit. But there was something unintentionally poignant in the title she chose for her son: “Eight Days a Week” is more time than can fit on the calendar. Ms. Zalkin’s baby, Hudson, born 13 weeks early, has had too little time.

As she sang, monitors showed Hudson’s heartbeat slowing and his oxygen saturation increasing. Effects like that were among the findings of a new study on the use of music as medicine.

Beth Israel Medical Center in New York City led the research, conducted in 11 hospitals, which found that live music can be beneficial to premature babies. In the study, music therapists helped parents transform their favorite tunes into lullabies.

The researchers concluded that live music, played or sung, helped to slow infants’ heartbeats, calm their breathing, improve sucking behaviors important for feeding, aid sleep and promote states of quiet alertness. Doctors and researchers say that by reducing stress and stabilizing vital signs, music can allow infants to devote more energy to normal development.