Choir singers not only harmonise their voices, they also synchronise their heartbeats, a study suggests.
Researchers in Sweden monitored the heart rates of singers as they performed a variety of choral works.
They found that as the members sang in unison, their pulses began to speed up and slow down at the same rate.
Writing in the journal Frontiers in Psychology, the scientists believe the synchrony occurs because the singers coordinate their breathing.
Dr Bjorn Vickhoff, from the Sahlgrenska Academy at Gothenburg University in Sweden, said: "The pulse goes down when you exhale and when you inhale it goes up.
"So when you are singing, you are singing on the air when you are exhaling so the heart rate would go down. And between the phrases you have to inhale and the pulse will go up.
"If this is so then heart rate would follow the structure of the song or the phrases, and this is what we measured and this is what we confirmed."
Sing from the heart
The scientists studied 15 choir members as they performed different types of songs.
They found that the more structured the work, the more the singers' heart rates increased or decreased together.
Slow chants, for example, produced the most synchrony.
The researchers also found that choral singing had the overall effect of slowing the heart rate.
This, they said, was another effect of the controlled breathing.
Dr Vickhoff explained: "When you exhale you activate the vagus nerve, we think, that goes from the brain stem to the heart. And when that is activated the heart beats slower."
The researchers now want to investigate whether singing could have an impact on our health.
"There have been studies on yoga breathing, which is very close to this, and also on guided breathing and they have seen long-terms effects on blood pressure... and they have seen that you can bring down your blood pressure.
"We speculate that it is possible singing could also be beneficial."