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When choir members sing together, it’s not just their voices that join in harmony.

According to a study published in the journal Frontiers of Neuroscience, when members of a choir sing together, their heart rates tend to synchronize and beat as one. A team of Swedish researchers led by Björn Vickhoff discovered that this synchronicity can produce a sense of calm that is similar to the effects of yoga.

It works like this: a long nerve called the vagus nerve — Latin for “wandering” — trails down from the brain stem into the body, where it influences the heart along with a handful of other organs. Exhaling activates the vagus nerve, which slows the heart’s pulse, Vickhoff says. So, if a group’s breathing is in sync, then it makes sense that the beating of their hearts will be too.

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“Singing is quite like guided breathing,” Vickhoff says. “If I would say to you, ‘Breathe in…breathe out,’ it would be quite as if you were singing a hymn in the church.”

The researchers asked 15 high school students to sing three different song structures while their pulses were recorded. By humming a song, singing a hymn, and chanting a slow manta, the choir members varied the synchronization of their breathing. The hymn required the most rigid breathing pattern, only allowing participants to breathe at the end of musical phrases, while the hum allowed participants to breathe at will. When students sang the hymn, their heart rates were the most in harmony.

The synchronized beating isn’t just of musical interest, says Vickhoff, since the finding could inform how singing might help some people to control their breathing and heart rate more effectively. Older people and those who are under stress tend to have less variability in their heart rates, a sign of poorer heart health since their hearts are less able to adjust to the body’s changing needs. Singing, however, brings a more consistent pattern to the changes in heart rate that follows the structure of the music, according to Rickard Åström, a musician who worked on the research team.

And the unified heart rates isn’t just symbolic — it has real, emotional effects. The vagus nerve that affects the heart has a serious hand in a person’s sense of arousal or calmness. “When people are singing slow songs together, waves of calming effect go through the choir,” Vickhoff says.

The researchers are hesitant to claim any long-term health effects yet, but Vickhoff says they are already preparing another experiment that will examine the effects of the synchrony on cooperation. He and Åström both suspect that choir singers are better at coordination and are more sensitive to one another after experiencing this physical synchrony. Their hope is to see if uniting heart rates can also unite hearts.

Watch the researchers discuss the study: