By Adam Brimelow
BBC News health correspondent
The classes are a big hit with patients
Doctors in London are investigating how singing can help seriously ill patients improve their breathing control.
Regular classes are being held at the Royal Brompton Hospital.
Hundreds of patients have joined the sessions, and 60 have been enrolled in a clinical trial which is expected to publish results by the end of the year.
Some patients who have joined the sessions say singing has transformed their lives.
Visitors to the Royal Brompton's Victoria Ward may be taken aback to hear the sound of music wafting down the corridor, together with banter, laughter and a cacophony of oral exercises.
This is a place that specialises in high-dependency care for patients with severe lung disease.
But it is also the venue for regular singing classes.
The voice trainer, Phoene Cave, says she is seeing improvements in breathing control even within one session.
"I'm helping them to become aware of their bodies in a way that they're not used to," she said.
"I'm helping them become aware of their breathing patterns in a way they're not used to, and I'm helping them to relax and expand and have fun and to laugh and to connect with other people. "
The class begins with some vocal limbering up, including collective sighing, buzzing noises and ha-ha sounds up and down the scales.
Then they move on to songs including "Drunken Sailor", "Cockles and Mussels" and "Kiss Me Honey Honey Kiss Me".
There is a party atmosphere, yet these men and women, young and old, have a range of lung disorders, including asthma, cystic fibrosis and emphysema.
For four years John Townsend, 69, has been living with severe chronic obstructive pulmonary disease (COPD) - a condition that kills 30,000 people in the UK every year.
He is connected to an oxygen supply at all times. He admits it has been a struggle just to keep going.
"You've just got to push yourself. You've got no choice," he said.
"Either you do that or you finish up lying in bed all the time. You give up."
John says the effect of singing has been staggering.
"Everything I do is now easier," he said.
"Hoovering, doing the washing, any chores, whatever you like.
"And basically I can do anything a normal person can do except I can't do it at speed. That's the difference."
It is a similar story for Doris Borucinski, 85, who has had debilitating lung disease for 30 years.
"My son said to me 'I can't believe that all this time you've been without any help and you go to one hospital and they do all this for you'.
"I started doing my own cleaning, washing, everything."
There are other singing groups for people with lung disease, but very few, if any, in hospital as part of NHS treatment.
It is clear the patients enjoy it. Researchers now want to assess its impact on breathing patterns and control, and are running a clinical trial.
Dr Nicholas Hopkinson, who is leading the study at the Royal Brompton, says there is a potential problem with trying to teach breathing techniques.
Patients sometimes become even more conscious of the struggle to get air in and out, and that can make matters worse.
"We have tried to approach it from the side, to train people to use their voice and their breathing for a different purpose, for singing, hoping that the skills that they gain through that in terms of controlling their breathing will actually be helpful in day-to-day life," he said.
The trial will finish in the autumn. It is hoped the results will be out by the end of the year.
But for patients like John Townsend the evidence is plain to see, and to hear.
"We get people from the wards coming and joining in," he said.
"You can hear it all the way along the wards. And people are cheerful. They don't say 'what's that singing?'.
"They become cheerful and they're not even singing. So of course it's a great thing."