This little piggy knows the (orchestral) score

It's not unusual to witness the Hong Kong Sinfonietta giving a passionate rendition of Wagner's Tannhauser Overture under the baton of music director Yip Wing-sie. Even if it's at 9am on a Monday in a local school hall. Nor is it strange to find the orchestra being filmed while performing.

What's extraordinary about this performance is that among the 64 musicians sits Canto-pop singer Ronald Cheng Chung-kei, trying to blow a French horn in between mouthfuls of noodles.

When the piece ends, the violinists (among them concert-master Elizabeth Lo Ka-yi) spring to their feet, followed by the wind section, then the rest of the ensemble, singing heartily a localised version of the children's tune Yellow Bird. 'Jaai lo mei, sai goh jau yi ging sik,' they sing. 'Jaai lo mei, ji jeng hai baai saan sik ...'

Although well known for its unconventional approach to classical music - including Yip giving audiences a brief introduction before every concert - the Hong Kong Sinfonietta hasn't gone off the rails.

Chief executive Margaret Yang says the ensemble's cameo in the latest, and third, instalment of the McDull movies, McDull, the Alumni, is groundbreaking. It's the first time the orchestra has been involved in a film, and the first time a local movie has featured a full professional western orchestra. It's also the first time humans have appeared alongside Hong Kong's favourite home-grown piglet.

If local film companies need an orchestra onscreen they usually use actors or freelance musicians - 'and the results are neither good nor authentic', Yang says. So when she heard that the McDull movie would feature a western orchestra, she thought the Sinfonietta should get involved.