The list goes on: improving sleep, toning facial muscles, improving posture, opening sinuses, releasing endorphins, boosting the immune system, reducing anger and anxiety, increasing self-esteem, reducing stress, promoting bonding.

"Singing in choirs is a forum for sharing, laughter and fun. And it provides a safe environment to try new skills," Engelmann says, and adds that the chance to sing can be a big drawcard for "reluctant students". "Singing is very important for children; an inclusive activity whereby all children can be equal and connected. And it's a fun way to spend an hour or so at school; those who might struggle with the more academic or theoretical aspects of learning can find that the pressure is off. There's no competition when having a sing-song at school."

There are other benefits at school, too.

"Singing helps children's memories. Practising musical patterns and rhythms helps form neurological pathways, with huge implications for children's learning."

And many Hong Kong schools employ singing to promote the concept of "international-mindedness" among students.

"Certain songs [not just national anthems] connect us to our cultures, our pasts and give us a sense of belonging. Singing songs from different cultures helps children to develop an international awareness, and is an excellent means of understanding different cultures and traditions."

Engelmann loves her role so much that she has founded two community choirs in Discovery Bay: DB Glee (for adults) and DB Glee for Kids, which includes acting and dancing training.

Canice Gleeson, director of music at the German Swiss International School, also leads choirs outside his day job, as director of Celtic Connections and vice-chairman of the International Schools Choral Music Society. "Music is in my bones. I knew from an early age it's the one thing that makes me happy."

Gleeson earned his music/teaching credentials at University College Cork and Newcastle University, and attended summer schools in conducting at New York University and at Juilliard.

"When you listen to a great musician perform a piece of music, if it's done with conviction and honesty it changes you. I continue to be inspired by the power of music."

Choristers in Gleeson's Celtic Connections come from all walks of life in Hong Kong and are of different ages, backgrounds and cultures.

"Preparing for concerts not only requires the discipline of attending weekly rehearsals, but it also develops the skills of listening, concentration, teamwork and developing confidence. Choirs bring people together with a sense of purpose and belonging to create music and communicate in ways that words can't."

Having worked with adults and students over the years, Gleeson describes singing as exhilarating, transformative and therapeutic. "It's like brain yoga. Singers develop breathing techniques to create phrasing and musical expression. This has many physical benefits, but it also transports the singer to another level, to a place where they no longer think about their day-to-day worries."

Gleeson has directed school choirs throughout his teaching career and agrees that the inclusive nature of choral singing is significant for children's education.

"Choirs truly know what teamwork means. Preparing for concerts and performances requires dedication, discipline and commitment. Through choral singing I see students develop self-esteem, confidence and the ability to communicate with each other as well as an audience. There is such an elevated sense of achievement during the rehearsal process when harmonies and the music come together. Singers learn to listen, concentrate and think creatively. These traits make for lifelong learners."

Bethan Greaves, director of Katterwall, trained as a chorister in Britain, singing in a school choir that performed at Westminster Abbey and on BBC Radio and television. After moving to Hong Kong she began conducting choirs with the Hong Kong Youth Arts Festival and the Cecilian Singers. She agrees with the benefits of singing, solo or in groups.

"The benefits include artistic fulfilment, creative and intellectual challenge, relaxation, the opportunity to perform and the chance to belong to a group without the need to run around. There seems to be a fairly steady stream of research emerging which indicates that singing in a group is possibly one of the best things you can do for body, mind and soul. I have 12 years worth of beautiful emails from choir members that testify to that."

In 2002, Greaves established Katterwall, which includes a studio in Sheung Wan where teachers work with students of all ages and abilities, and in a variety of styles including opera, jazz and pop. There are several amateur choirs under the Kassia umbrella.

"We run Kassia Women's Choir, Kassia Men's Chorus, Kassia Youth for 13 to 18 year olds, Hullaballoo for five to eight year olds, and soon will be running a new group for three to five year olds."

Greaves has also established the Soho Collective, which acts as a booking agency. Her fellow singers have been involved in many productions over the years, and she also organises short-term choral groups for specific projects.

But there are challenges for particular groups. "Aiming choirs at teenagers is a challenge as they are so incredibly busy with schoolwork. Getting sufficient men to be able to commit to regular rehearsals, when so many of them travel as part of their working life, is a constant challenge, too."