C AllStar do not churn out karaoke-friendly ballads like most boy bands. Far from it. Since the release of their debut album Make it Happen (2010), the predominently a capella quartet - Andy Leung Chiu-fung, Kenny Chan Kin-on, Jase Ho and King Wu - have been focusing on contemplative songs that share the sentiments of a city undergoing many social and political changes.
On Our Tram, Don't Let the Island Sink and Music Colony look at how certain aspects of Hong Kong life have disappeared in recent years. The songs are tinged with nostalgia, something that's unusual for a group with an average age of 26.
Their upcoming "Our Woodstock" concert has a retro feel to it, too. Exploring the history of their home city, as well as that of their families, has been an important part of C AllStar's musical journey. "Finding our roots is a simple and natural direction for us. Like at school, we all have to study history.
"We learn what happened in the past so we are able to understand why we are sitting here today," says Chan, a former professional footballer with Hong Kong 08 and Hong Kong Rangers.
"I wanted to know where my parents came from, and how they grew up. Learning this has given me a sense of belonging, and helped me fall in love with where I live," he says.
But after five albums, critics have questioned whether the band have overplayed their nostalgic and sentimental style. Some claim their music has become trite and repetitive.
That's not how Chan sees it. "That's like saying, 'Jason Mraz sings a love song again,'" he says. "But there are many different kinds of love song, and so many different ways to deliver your message."
Leung brushes off the criticism, saying that they do not feel they are repeating themselves: "When we think we have done enough, we will move on," he says.
Jase Ho, the group's beatboxer, believes they are doing what comes naturally. "We are Hong Kong people. If we don't sing about Hong Kong, what do we sing about? It's totally natural we do that," he says. "You can tear a building down, but songs and videos are there forever."
Ho is referring to the video clip for their latest song Time Flies. This was partly shot at Wah Fu Estate, a 47-year-old public housing complex that is being considered for redevelopment.
"Things change so rapidly," Ho says. "We don't know if the Wah Fu Estate will still be here in the future, but at least we have the video to remember it."
The band are all university graduates. Leung studied at City University, Chan at the Polytechnic University, Ho at Baptist University and Wu at Private Hualian University of Guangzhou.
They share a strong sense of social awareness that comes through in songs such as We Will Live as One, which touches on the issue of gay rights in Hong Kong.
The boys also have a major gripe about the way the opening hours of the pedestrian zone at Sai Yeung Choi Street South in Mong Kok have been restricted to weekends and holidays since January.
Street performers have complained about the loss of a platform, something which resonates with the band. C AllStar spent a lot of time performing on the street, promoting themselves and practising in their early days.
Chan describes shortening the opening hours as "tearing down their playground". But he also says it has shown the resilience of the performers.
"I was in Mong Kok last week and I saw performers in another space," he says. "That's the Hong Kong way. If someone wants to do something badly enough, they will find a way."
Ho is more straightforward. "If you tear my playground down, please build me a new one. I don't think Mong Kok is the best place for playing street music anyway. If you block this street, give us somewhere else."
The band where were struck by the street culture on display in Paris during a trip abroad. Street music is part of a wider culture, they feel, noting that the French treated performers with a lot more respect than they do here. "It is normal to give money after a street performance. It is done out of respect," says Chan.
C AllStar have come a long way since their busking days in Mong Kok. They first met at a local singing contest in 2009, where they were the four semi-finalists. They created such a buzz at the event that record label Kingdom C Productions decided to sign them as a group.
Since their chart hit Sky Ladder in 2010, they have become one of the most popular local groups.
The band's music has also progressed in recent years. Their latest album, titled Cantopopsibility, was released last October, and demonstrates that Canto-pop, as a genre, is full of possibilities.
With help from producer Kan King-che, it displays a range of musical styles including trance, traditional Chinese folk, bossa nova, rap and R&B.
The group has brought in producer and former Swing member Jerald Chan as musical director for the concert, which is named after their 2011 sophomore album. C AllStar promise their old tunes will be transformed by Chan's "magic wand".
Their songs may be as socially relevant as before, but it sounds like their music is about to take a new direction.
C AllStar, Mar 23, Hong Kong Coliseum, Hung Hom, 8.15pm, HK$250, HK$380 and HK$550. Inquiries: 2905 8134