When he was first approached by the show's producers to join last year, he said no as he was filming the fantasy action television series Halfworlds.
Approached again this year, he was still reluctant.
"The biggest thing that I was afraid of was failure. I was already a fairly established musician, so to put yourself on a competition stage, that is to put in question your ability, your legitimacy as a musician," Hartono, 25, tells The Straits Times.
Eventually, he decided to take the leap.
"I didn't like how scared I was of it. I didn't like that this was something I didn't want to do because I didn't think I was able to do."
He was confident of making it to the first round, though.
"I thought it was going to be like auditions, maybe one round, and I'm done. The talent pool there is insane."
He himself is no slouch in the talent department. Despite his young age, he is already a veteran of the local music scene. His first major concert was 2005's ChildAid show, which is organised by The Straits Times and The Business Times. He released his debut album, Let Me Sing! Life, Love And All That Jazz, in 2006 and, most recently, held a solo gig at the Esplanade in July.
Because of his jazz background, he would often improvise during the Sing! China competition, be it during rehearsals or at the actual performances. The technical crew soon gave up trying to make him stick to a fixed rundown.
But his adventurousness meant that he was a great fit for contest judge and Mandopop king Jay Chou's team. Hartono says: "Beyond anything else, he likes to innovate, experiment and push his own boundaries. He's always challenging the perception of what Chinese music should sound like.
"And that's what I learnt the most from him more than anything else. No matter what level you're at, never be comfortable, always want to do more."
Chou has extended an offer to Hartono and all his other mentees, that if he ever goes to their hometowns for a gig, they were going on stage with him.
Hartono adds: "Beyond that, we've spoken about the potential of working together in the future. I don't not too sure what the projects will be yet but there's definitely interest both on his side and his team."
His more immediate plans include putting out an EP under Warner Music, which should include at least one Chinese song.
It will not be one of the numbers he sang during Sing! China but an original song composed by him, with someone else contributing lyrics.
"I'm incapable of writing Chinese lyrics at the moment. I can speak in the language but I can't be lyrical and poetic in it just yet."
This article was first published on October 11, 2016.
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