The Requiem, which combines Japanese Haiku poems and Latin text with a dash of jazz-rock, is dedicated to the victims of last year's tsunami in Japan.
Welsh-born Jenkins, who started out as a jazz musician and composer of music for advertising and film, now writes classical music that often combines ethnic vocals and percussion.
Jamie, who studies at the German Swiss International School, in Pok Fu Lam, is keen to meet Jenkins, who chose him to sing after being sent a recording of his singing during auditions.
"I feel very honoured to sing in Karl Jenkins' piece," Jamie says. "I find his music amazing - so different from other composers. I found this Requiem very dramatic and touching."
Born in Hong Kong to a mainland father and a British mother, Jamie speaks both Putonghua and English. His singing talents were spotted by a music teacher when he was at kindergarten. "My teacher told my mum I had a very good voice," he says.
Soon Jamie was performing with different choirs in Hong Kong, Beijing and - in 2010 - in Austria with the Vienna Boys' Choir. He is already an experienced soloist in Hong Kong, having sung Faure's Pie Jesu at St John's Cathedral, The Snowman with the City Chamber Orchestra, and in the musical Guys and Dolls last year. He also performs regularly at the Fusion Performing Arts Academy in Hong Kong.
Singing on stage feels a natural, rather than daunting, experience, he says. "When I sing, I feel calm and relaxed. It takes away the pressure from school work and makes me happy."
To prevent any nerves, he has a little ritual before going on stage. "I take 10 deep breaths. It always works," he says.
If he does make the odd mistake during long, complicated pieces, he has learned a way to get around it and stay calm.
"Once I was on stage and forgot a line, so I repeated what I sang before," he says. "Sometimes, if that happens, I hold a note longer, too. The most important thing is not to look like I've made a mistake, but try to smooth it over. I learned [it] from my teacher."
Jamie does vocal exercises up to three hours per day and takes regular vocal lessons from two private teachers to improve his technique. He also avoids strenuous sports or eating junk food, which could harm his voice.
In future, he hopes to have a career as a singer or in the performing arts. "I can't imagine myself getting tired of singing. I think if I try hard and keep looking for opportunities, I will be able to succeed."