Musicians On Call, a nonprofit providing live music to the seriously ill, hopes to aggressively expand to other major cities across the U.S. next year.

For more than a decade, volunteer artists with Musicians On Call have given bedside performances to patients undergoing treatment or unable to leave their hospital beds.

"It's a very tangible way to give back," Pete Griffin, president of Musicians On Call, told Reuters Health. "We are not music therapy, because that is its own medical profession. What we do is bring live music, and what a lot of research shows is that that does decrease patients' stress levels and lowers blood pressure." Family members may also benefit from seeing their loved ones enjoy a "moment of normalcy."

Since 1999, Musician On Call volunteers have performed for more than 415,000 patients in hospitals, nursing homes and hospices - but only in a handful of states.

Griffin said the organization hopes to aggressively grow throughout 2015 and expand beyond its seven "hubs" where most Music On Call programs are located: New York, Philadelphia, Baltimore, Washington, D.C., Miami, Nashville and Los Angeles.

For hospitals without the bedside concert program, Musicians On Call provides a collection of albums.

"We create 'music pharmacies.' We have supporters and record labels who donate CDs, and then hospitals go on our website and request a 'music pharmacy,' a box of 200 CDs and CD players for their patients to listen to," Griffin said. Nearly 800 hospitals have requested them.

Dr. Melinda R. Ring, an assistant professor of clinical medicine at Northwestern University's Feinberg School of Medicine in Chicago, said she believes music helps provide the seriously ill a sense of peace.

"Music touches us. Music has the ability to transform the mood that we're in, the way we're perceiving things," Ring told Reuters Health. "For somebody who has fears about death, pain or other end-of-life issues, listening to something that can bring them joy in the hospital doesn't necessarily change the outcome of what will happen, but it changes their experience."

Loretta Downs, past president of the Chicago End-of-Life Care Coalition and a hospice volunteer, said she would like to see more medical centers supporting Musicians On Call.

"Music is a form of reminiscence, and if a family member or a patient can request a song that brings back positive memories, it's a great thing," Downs told Reuters Health. "We want to remember the things that made us happy."

Downs founded Chrysalis End-of-Life Inspirations, an effort aiming to equip hospitals and nursing homes with "Chrysalis Rooms," private spaces where seriously ill patients can gather with family and friends and listen to music, among other things.

Many artists visiting hospitals through Musicians On Call find themselves playing requests for upbeat pop songs. Currently, the most popular request from young people is "Let It Go," the Oscar-winning anthem from the animated film "Frozen."

"When we go into the children's hospitals, a lot of them know the Disney songs," Griffin added. "With the older populations, blues and classic rock are popular. Country music is popular around Nashville, rock in the Northeast."

Singer and songwriter Kenli Mattus was one of the first artists to work with Musicians On Call.

“I really enjoy giving patients what I think they want. For kids, I play nursery rhyme songs or make up songs on the spot, which they really like. When I play for adults, I play Frank Sinatra, soul or gospel.” Mattus told Reuters Health. “When you go room-to-room and play for a handful of people, it’s an incredible personal connection. It really inspires me and makes me feel like I’m doing something good for the world.”

Other notable artists who have performed with Musicians On Call include Pharrell Williams, Kelly Clarkson and Paulina Rubio.