Cody Wise goes from YouTube to UK No.1

He's No.1 in the UK and for Cody Wise it all started with just one song on YouTube and a bit of help from Will.i.am.

With his rendition of the Jackson Five's Who's Loving You at a concert called Fam Jams in his native city Philadelphia, a then 13-year-old Wise caught the attention of superstar Will.i.am.

"A producer that he was working with at the time named Jean Baptiste showed him my video and he flew me out to California and we ended up meeting and hanging out and bonding," Wise told AAP in Sydney.

The singer, who is now 18 and has spent the last 4-5 years honing his musical skills with Will.i.am, is in Sydney to promote his song It's My Birthday.

The pair's hit collaboration evolved from a Bollywood song, a genre Wise admits he really loves.

"It isn't a cover, it's interpolated from A.R Rahman's Urvasi Urvasi, which is actually one of my favourite songs," Wise said.

"When we were coming up with the song we were watching the video and thought it was amazing."

Wise said at first he was alone on the song and then will decided to put some verses on it.

"Then it sounded amazing," he said.

"Will's like a mad scientist. The moment he hears something he goes into mad scientist mode, especially in the studio. We end up coming up with stuff out of nowhere," he said.

The pair are now riding high in the UK charts but Wise revealed that pesky time differences meant he had to celebrate his success quietly and on his own.

"I was in America at the time and Will tweeted me and he was like `Yo, it's No.1 in the UK, it definitely won't be your last.'

"I remember it was, like, 4am when he did this and I freaked out, I didn't believe it...but it was 4am and I was about to go to bed. But then I couldn't go to bed because I was so excited," Wise said.

"I couldn't tell my parents or anything because they were all asleep. So I had a little internal Cody freak-out party in my room."

However, the singer will be able to sing his song loud and proud when he performs on the Nine Network's The Voice on Monday night.

"When we did this song, we pretty much knew instantly that it was a smash," he said.