Music isn't the only attraction at these get-togethers. Whether in the form of weekend singalongs beside the Shing Mun River at Sha Tin, an early morning chorus in Tuen Mun's Butterfly Beach, or Sunday concerts in parks from Yuen Long to Kwun Tong, the groups have become vital forms of assembly that nurture a community spirit among often-alienated new town residents.

Besides the obvious attractions of fresh air and a green, relaxing environment, they give residents the opportunity to strike up easy conversations, join the singing, or perform as the mood takes them, but without the pressure of having to fit into an organisation.

With about 10 groups springing up in the past four years, Tuen Mun Park has the liveliest music scene. No one's sure when the amateur musicians first started performing, but elderly saxophonist Lee Kam-fook reckons he's the pioneer. 'I was the first and only one,' Lee says. 'In 1981, I started playing accordion in the park. Several others soon followed me.'

The trend didn't take off until 2001, when a group of retirees and unemployed formed Great Sounds, or Leung Sing, and other music lovers followed suit. Soon, Tuen Mun Park was humming with music, chatter and laughter, from morning till night. The amateur musicians attracted curious audiences from as far away as Tseung Kwan O and Tsuen Wan.

Under a bridge, retiree Yu Shi-fu, 72, hands out microphones to his usual, 10-strong audience to sing along to his cassette player. In a nearby pagoda, the Blue Sky gang warble Sam Hui Koon-kit's old Canto-pop hits. There are also Cantonese opera groups and individuals playing traditional Chinese melodies on flutes and erhu.

Indonesia-born Leung and friends form one of the most popular groups, mainly because anyone who wants to perform can join them on the spot. This band with no name arose from a casual conversation guitarist Leung had with his friend and drummer Ho Chang-ie, who was also born in Indonesia. 'We thought of playing some Indonesian songs,' says Leung. The pair quickly drew listeners with their repertoire of Indonesian and Malaysian folk songs and 1950s and 60s Putonghua hits.

'Sometimes, there were over 100 in the audience,' says Leung, whose group swelled to eight and then 10. 'Most of us are retirees in our 60s and 70s. Some are housewives and new migrants.'

He was soon performing four afternoons each week. 'When I play music, I forget all my troubles,' he says. Initially, Leung's new passion didn't go down well with his wife, Siu Yuk-yin, 58, but she changed her mind when she saw the sessions for herself. 'I found it so much fun,' she says.

'We were invited to play at an old people's home. Old folks were pushed out in wheelchairs to listen to us, and people from other districts came to see us.'

The sessions in the park have given a sparkle to otherwise humdrum, even lonely lives. Since Siu joined in the fun a year ago, she's become a daily presence at their regular corner each afternoon, returning home at dusk. With all the singing and dancing, her blood pressure has improved, too. 'I rarely get sick,' Siu says. 'We love it so much. It gives us a carnival feeling.'

Retiree Ng Kong, 71, feels similarly rejuvenated. 'The songs were what I listened to when I was young,' he says with a smile. 'I feel as if I've returned to my youth.' The former garment worker says he used to feel 'unwanted' after he retired in 1999, but the sessions in the park changed his life. 'Now, each day I have something to do, and feel very positive,' Ng says. 'My children and wife are so relieved.'

The groups are under threat, however. Over the past two months, city officials have cracked down on their activities, saying the elderly musicians have annoyed people. Leung and Siu were arrested on May 21, although the police dropped the charges this month.

Since then, many of the park ensembles haven't dared to resume their performances. Some mooch at home; others wander disconsolately in the park, their indignation rising whenever they pass their usual haunts.

'I feel very unhappy,' Ng says. 'I hope the government can let us continue to sing and play.'

The Leisure and Cultural Services Department defends its actions, saying it was responding to complaints by other residents. Margrit Li, a department official, says the LCSD has received 149 complaints since 2003. Many are repeat calls, she says. 'Our staff thought the bands were too loud, and there were many complaints about the noise,' Li says. In the absence of a set standard for park-noise levels, it's up to officers' discretion to enforce the municipal ordinances.

Trend Plaza resident J. Choy says he's complained 30 times. Since 2003, he's called the Tuen Mun Park management almost weekly. 'I was disturbed by their noise every day,' Choy says. 'There are four roads and two tracks between our building and the park, but we can still hear the sounds. You can imagine how loud it is. I don't mean that people can't play music in the park. The point is they must keep the volume down. They won't disturb us if they play without loudspeakers.'

Leung says it's difficult to perform to a crowd in an open space without amplifiers, but he promises to get his group to lower the volume and stop using some of the equipment.

Similar clashes have in Tin Shui Wai - a low-income district - where new migrants and local workers gather nightly for a couple of hours' free music by the nullah at Tin Chak Estate.

'When I listen to the old songs, I remember my life on the mainland,' says Man Choi-ha, a music-session regular.

Tin Shui Wai police say they've received almost 200 complaints about the groups from nearby residents over the past year. Last year, district board members and the groups requested that noise barriers be built to allow the music sessions to continue, but the Home Affairs Department has yet to reply.

Meanwhile, despite official banners warning that performers could face a $2,000 fine and a fortnight's jail, the Tuen Mun musicians have been told they can perform as long as there aren't any complaints.

Siu, who resumed singing in the park last Sunday, is delighted - but still worried. 'If just one person complains about noise, how will the officers handle it?' she says. 'I'm afraid that I would be prosecuted again.'

Additional reporting by Fanny Wu