BIRMINGHAM, Ala.

The persistent beeping catches Sunny Speaker's attention. She quickly steps around nurses, incubators and bulky machines while balancing a stack of patient charts -- and a guitar.

The beeping is coming from the monitor on a premature baby boy who is struggling to breathe because of respiratory disease and whose blood is getting low on oxygen.

Speaker settles next to him with her guitar, opens the hatch to his incubator and softly begins to sing a lullaby.

"This little light of mine, I'm gonna let it shine, even in a hospital, I'm gonna let it shine," she sings.

After just 10 seconds, the baby's heaving chest begins to calm, his breathing gets deeper and the oxygen level returns to normal.

"He responds to more varied melodies," Speaker says softly as she keeps playing a repertoire that includes such familiar refrains as "Twinkle, Twinkle, Little Star." The 29-year-old is the in-house music therapist at the University of Alabama-Birmingham Hospital and the only medical music therapist in the state. After five years treating patients with cancer, Alzheimer's disease and psychiatric disorders, she now is in the hospital's critical-care nursery.

Stimulating development in premature babies is at the forefront of research in music therapy, a field that has traditionally helped mentally retarded, psychotic or dementia patients express emotions and thoughts.

Florida State University researcher Jayne Standley has found that music therapy may lead to speedier neurological development in premature babies, and those with consistent music therapy have shown enough improvements during research studies to go home up to a week earlier than other preemies.

Speaker says Standley's work inspired her to persuade the doctors and nurses at UAB's critical-care nursery to give music therapy a try.

"It's the first time I've worked with infants that are sick," Speaker says. "I had no idea how dramatic it would be." Speaker's "lullaby group" includes underdeveloped babies -- often weighing no more than a couple of pounds -- who suffer from respiratory diseases. She hopes her live music helps them breathe more deeply and consistently. She's found that lullabies gently stimulate babies to take breaths and smoothes out the irritating background noise, which relaxes them enough to breathe to a regular rhythm.

Ultimately, she wants the babies to breathe regularly on their own.

Dr. Lance Prince, who works with the babies at UAB's critical care unit, says music therapy brings peace to the stressful environment of the ward and helps babies adjust to the everyday sounds they'll encounter when they go home.

"If you're a baby and you hear this noise all day, every day," he says, referring to the beepings and alarms of the monitors. "It's nice to hear something above all the craziness." He recalled a day earlier this month, when several of the babies were crying and the machines sounded off on low oxygen levels. Amid the chaos, Speaker began to sing.

"All of a sudden, everything kind of stabilized," he says. "It's rare to get such a moment." Speaker says she's also received warm reactions from parents, who often motion her over to sing a lullaby.

Leandria Burrough, whose daughter Keyli was born two months prematurely at 3 pounds, 6 ounces, says Speaker's singing helped during a stressful time.

"There's so much going on with a premature baby -- it can make you cry," says Burrough, after cradling Keyli while Speaker sang. "I though they were just going to pop a CD in. They have a live person -- that is so special." Burrough says Keyli responds to the music by opening her eyes and recognizing her face.

Parents of premature babies "don't get much bonding," Speaker says. "The more bonding they have, the more progress they make developmentally. And that relaxes the mothers." Speaker says having live music is crucial to effective music therapy, especially for infants, who follow the singer's facial expressions and hand movements. At the same time, the performer can observe the infants' reactions and adjust the music.

Speaker is not a doctor. Before passing a board certification exam to work in the hospital, she earned a bachelor's degree in music therapy from the University of Alabama. The program combines music with the study of human anatomy, biology, psychology and other classes that focus on the responsibilities of a therapist.

Speaker's caseload carries more than 70 patients spread over several wards, including cancer, geriatric and mental health units. She says her duties encompass everything from singing lullabies to infants to singing at funerals of patients.

She doesn't worry about getting too close to her patients -- it's what she's supposed to do.

"Part of our job is helping with the emotions, therapy, family members dying," Speaker says.

She says doctors often don't have the time to fulfill their patients' personal needs. "You can't just treat the kidney -- you have to treat the whole person. Luckily, most doctors realize that."

And that's why they call her in.

On a recent gray, damp afternoon, she stopped by Priscilla Allen's room in the bone-marrow transplant unit after a busy session with the "lullaby group." The 50-year-old Allen, tucked tightly in sheets, motioned for Speaker to enter her dimly lit room. Allen says she's looking forward to rehab treatments the following week.

"What would help you today?" Speaker asked cheerfully.

"There seems to be a light at the end of the tunnel, finally. Think about that," Allen answered.

Speaker crooned a set, wrapping up with the Beatles' "Here Comes the Sun."