Many people feel happy after singing. Scientists wanted to know why. In Germany, choir members sang together, and then researchers checked their saliva, the water in their mouths.

After singing, they had more of a substance that helps protect the body. They also felt better. In Britain, people in a singing class became friends faster than people in other classes. But these studies were small, so we need more research.

Why do we often feel refreshed after singing? Researchers have tried to answer this question by measuring singers' saliva, heart rates and relationships. Most of these studies were small, so singing cannot yet be called a proven health treatment. In a 2004 German study, members of an amateur choir either sang or only listened to choir music.

After singing, their saliva contained more of an immune substance called secretory IgA, and their mood improved. In Sweden, researchers found that when healthy 18-year-olds sang slow songs with regular breathing, their heart rate patterns became similar. In Britain, adult education students in a singing class felt closer to each other after just one month than students in craft or creative writing classes.

Most research on singing and health is small, and much of it lacks a proper control group. Some of the experiments are clever, though. In a 2004 German study, members of an amateur choir came in for two sessions a week apart. In one they rehearsed choral music, and in the other they only listened to it.

Singing raised levels of secretory IgA, an antibody in saliva that helps defend the mouth and nose against pathogens, and improved mood. What such a rise in a saliva marker means for health is not known. Listening lowered the stress hormone cortisol but actually increased negative feelings. Swedish researchers later found that slow songs with regular phrasing brought singers' heart rate variability patterns into line with one another, probably because singing is basically a structured breathing exercise.

Over seven months, British adult learners in singing classes felt closer to their classmates after the first month than those in craft or writing classes did. The other groups caught up by month three, and the researchers called this an "ice-breaker effect." In a 2022 randomized trial, an online breathing program developed with an opera company improved mental-health-related quality of life in people with long COVID.