In treating Canadian soldiers returning from the First World War with psychological wounds, British musician Margaret Anderton discovered music does indeed have “charms to soothe the savage breast.”

“Wood instruments,” she observed, “are particularly potent for a certain kind of war-neurosis because of their penetrating, sustained tone.” Anderton went on to teach the first music therapy course at Columbia University.

But neither she, nor the poet William Congreve who coined the phrase two centuries earlier, would have had any idea that such soothing sounds are more than music to the ears. Music can help remodel an injured brain.

Modern scanning technology that reveals the inner workings of the brain has provided evidence of the effectiveness of music therapy. It is now used widely in the U.S. military health system for treating brain and psychological injuries, in rehabilitating speech and language deficits, improving interpersonal communications, increasing motor control, improving attention, facilitating multitasking, regulating emotions, for relaxation and stress relief, increasing noise or sound tolerance, and promoting familial bonding and social engagement.

But how could drumming, singing or learning to play an instrument achieve any of that?

Decoding music, which is what your brain does as you listen, is a complex cognitive function. Functional MRI imaging shows music sparks regions throughout the brain to communicate with one another. Looking at the scans, you might say music lights up the whole brain.

Music activates a number of networks across the brain, including those that govern emotions, memory and motor control. For instance, language and musical melody activate similar areas of the brain and music causes brain activity similar to emotions caused by other stimuli.

Rhythm stimulates areas associated with movement, which may explain unconscious toe-tapping and spontaneous dancing. Brain areas associated with mind-wandering and creativity are associated with processing of musical sound. Areas associated with understanding language are used in processing music.

“Biomedical researchers have found that music is a highly structured auditory language involving complex perception, cognition and motor control in the brain. It can effectively be used to retrain and re-educate the injured brain,” wrote Michael Thaut and Gerald McIntosh in an online article for the Dana Foundation, which supports brain research.

Music therapy gains a back entrance to shared areas in an injured brain, where it can take advantage of neuroplasticity, the brain’s ability to reorganize connections in response to learning, effectively rewiring some functions.

“For example,” explained Thaut and McIntosh, “music tends to activate brain structures either bilaterally—in both hemispheres simultaneously—or in the right hemisphere more than the left. For injuries on one side of the brain, music may create more flexible neural resources to train or relearn functions. Aphasia rehabilitation is a good example.”

Aphasia is an impairment in producing or comprehending speech. “Singing—which relies mainly on right-hemisphere brain systems—can bypass injured left-hemisphere speech centres to help people produce speech.” That is also one explanation of how a person who stutters does not do so while singing.

Similar results have been achieved by involving the shared brain systems for rhythm and motor control to help rehabilitate Parkinson’s patients to walk again, by learning to synchronize steps to a sensory timer, as dancers do in response to the timing in music.

Blast injury and PTSD damages white matter and connective tissue, disrupting processes in multiple brain regions. “Studies suggest that music can impact multiple neural networks simultaneously and can assist with rebuilding connections between various regions of the brain,” said an article in Music Therapy Perspectives.

Now researchers are studying the use of music for control of mood and emotions in people with traumatic brain and post-traumatic stress injuries.

Soldiers are already familiar with music for self-soothing.

“The scientific community has come to understand that listening to music is much more than an emotional endeavour,” Kip Pegley of Queen’s University’s School of Drama and Music said in a 2015 article in the Journal of Military, Veteran and Family Health.

In a series of interviews with serving military, Pegley discovered that music is used by soldiers on deployment to help them cope with dangerous, noisy and stressful environments. Listening to a personalized music mix helps evoke feelings associated with home, reducing feelings of isolation and making them feel safer.

Music, especially heard through headphones, “enabled soldiers to create walls where none existed and extend precious moments of sonic privacy that helped alleviate their continuous hyperarousal.”  The soldiers weren’t tuning out, he said, but “gaining more control of their environment and their responses to it—from the inside out.”