Originally from an interview with Jenna Birch at Fitbit 

WHAT DO YOU NEED TO KNOW ABOUT MUSIC’S EFFECT ON YOU?
The potential benefits of music as a therapeutic and healing tool are endless! The ways that music affects you can have a big impact on health, happiness and personal growth, or they can just be a way to reduce stress and enhance mood. Some of the specifics about music include:
-This is Your Brain on Music” (Plume/Penguin, 2007) tells us that listening to and playing music increases the body’s production of the antibody immunoglobulin A and natural killer cells — the cells that attack invading viruses and boost the immune system’s effectiveness. Music also reduces levels of the stress hormone cortisol.
Read more