The strumming of a guitar echoes down a corridor as the music therapy session begins at Penn State Children's Hospital in Hershey, Pennsylvania. Jan Stouffer greets several kids from the cancer unit, who range in age from 10 months to 11 years.

"Hello friends," she sings, "my name is Jan. We're gonna make music…we'll sing together and play, we'll have a good time today. Give yourselves a hand!"

Penn State Milton S. Hershey Medical Center complex

Ms. Stouffer is one of about 5,000 music therapists who are using music to boost the power of traditional medicine in rehabilitation hospitals, nursing homes, senior centers and schools throughout the United States.

The children sit in a semi-circle facing her, surrounded by an array of drums, bells, tambourines, maracas and other musical instruments. Ms. Stouffer helps each of them pick the one they'd like to play.

"Do you want the frog shaker or the bear tambourine or would you like a drum," she asks a little boy, who opts for a drum. "The really big one," he says. "I thought so," responds Ms. Stouffer, laughing while handing him the drum.

Julia Martin chooses an instrument

These children spend most of their time alone in sterile hospital rooms. Ms. Stouffer says being with other kids in a music therapy session eases stress while helping the young patients get stronger, more active and more expressive. "I provide a lot of activities for them to engage in self expression, to share their ideas, to come up with lyrics to songs…that type of thing," she says.

While it may seem as if her session is loosely organized, the therapist reveals that the opposite is true. "The structure of the music activities and the planning that goes into what music you're going to use and how you're going to use it -- that's what differentiates music therapy from performance, entertainment, recreational music," she explains. "We have very clearly defined goals where we're using very specific music in a very specific manner to work on their goals."

Patient Emma Jean Rushton and her sister Sarah join in stick therapy

For example, the youngsters are given sticks. "Tap your sticks together…tap, tap, tap," Ms. Stouffer instructs them. "Can you reach your arms way up high with your sticks? Do you want to play down low?" The music therapist says this exercise was carefully constructed. "I decided to do a sticking activity and included opportunities to play the sticks in different directions at different heights to their body in order to include strengthening and physical conditioning into the activity," she says.

While she performs much of her therapy individually, in patients' rooms, Jan Stouffer says the weekly group session is special because it keeps the kids involved and attentive. In one activity, she singles out each child individually by the instrument he or she selected.

"We are going to give everybody a chance to solo and be a star," she tells the kids. "Listen carefully to what instrument I call for and just that instrument plays." Then she begins a song. "We are great musicians," she chants. "People come from miles away just to hear us play . . . the cabaca!"

In response, 11-year-old Caitlin shakes the rattles enthusiastically, seeming to be oblivious to the clear plastic tube running from her arm to an IV stand. "Listen to Caitlin play the cabaca," Ms. Stouffer says. "Let's hear it for Caitlin!"

Caitlin doubles with therapist Jan Stouffer on the xylophone

The youngster says she joins the group whenever she's able, calling it a nice change from her usual hospital routine. "I like playing the musical instruments," she says. "It's a lot of fun. I like the drums, personally. I feel like I get a little more energy."

Family members are welcome to join the one-hour sessions. Caitlin's mother, Darlene, often does, and says she enjoys it. "I love to see the difference from the arrival until the time they leave," she says, watching her daughter singing happily in her wheelchair. "You see the big difference in their faces. They light up while they're singing. It kind of takes them away from the pain and suffering. It takes you to a different place, even though you're at the hospital."