Singaporean singer Nathan Hartono expected only to have "a cool story to tell in the future" when he auditioned for Sing! China, a popular reality singing competition.

He ended up having a mentor in Mandopop king Jay Chou, who even raised the possibility of the two performing together in Singapore, during the show, which aired last Friday night on China's Zhejiang Television.

"I am realistic. I know I can sing, but I expected almost nothing, maybe some exposure. After all, it's China, with a gigantic amount of talent," Hartono, 25, tells The Straits Times.

The jazz singer-songwriter, who has also done some acting, is the first Singaporean known to have made it past the televised auditions, where the celebrity judges do not come face to face with the performers until they hit a buzzer showing their approval.

Hartono's modest aspirations partly stemmed from the fact that he has not always been comfortable speaking in Mandarin.

"My default sometimes for conversations (in Chinese) would be not knowing what to say," he says.

He is of Indonesian-Chinese parentage and studied at Nanyang Primary School and Anglo-Chinese School (Barker Road).

While he has been brushing up on his Chinese in recent years, he says he is still figuring out how to use his account on Sina Weibo, a popular social media platform in China, which he set up only last week.

In fact, the singer, who agreed to do Sing! China after its producers approached him for the second time, was fluent in his debut performance in China and impressed all four music megastar judges.

Chou and the other judges - Harlem Yu, Na Ying and Wang Feng - lauded his golden-boy appeal. Singer Na Ying asked him for a hug and praised his "warm and honest" performance and good looks.

Chou nodded his head in appreciation during Hartono's R&B-inflected version of You Mei You (Have You Ever?) by Taiwanese singer Wei Li An. After Hartono chose Chou as his mentor, the two exchanged a fist bump and hug.

It was an enthusiastic reception echoed by fans of Hartono's performance, who say he has done Singapore proud.

Mr Christiano Choo, 42, the co-founder and creative director of a wine and gift service firm, says: "We were very proud of the moment when all four judges picked him. He sang better than the original singer in his rendition, which is already looping in people's playlists, including mine.

"He is everything in a package: looks, unique voice and charisma. He will possibly gain new fans in China. The rest depends on how Jay is going to help him against the other teams and if Nathan can withstand the pressure."

Hartono says that having all four judges want to work with him was "a really nice surprise".

He had already decided beforehand that, if Chou picked him, he would take up his mentorship.

"A lot of it had to do with songwriting, which I've also been doing," he says, adding that he admired Chou's "work ethic, drive and creativity".

Hartono also has the drive to excel, says a friend and manager of many years. "I work with many artists and he's very hardworking, serious and self-motivated about his music," says Mr Lim Sek, chief executive of Music and Movement, an entertainment company.

He has known the singer since he was about 14, when he won the local Teenage Icon talent contest in 2005 and signed on with Mr Lim's firm for a few years.

In 2006, Hartono released his debut album, Let Me Sing! Life, Love And All That Jazz. During his teen years, he also performed twice at the annual ChildAid charity concerts, organised by The Straits Times and The Business Times.

His latest concert was a solo gig at the Esplanade on July 9.

Mr Lim calls Hartono's parents - resort consultant Thomas Hartono and Madam Jocelyn Tjioe, a senior vice-president of TungLok Group - "one of the best parents I've seen in entertainment".

"They're very encouraging, but they don't get in his way. They're not the type who say you go and be a lawyer," he adds.

Hartono, who has an older brother and younger sister, studied music production and engineering at Berklee College of Music in Boston.

His demeanour is down-to-earth and grounded. "My musical dream is simple, to make music as best I can, to let things happen."