His songs -- including hits like "Lights Are On", "It's OK" and "Go Solo" -- have been used on 1.6 million TikTok videos, driving fans to other music services where he has picked up hundreds of millions of streams.

Rosenthal gave AFP a few tips on the secrets of his TikTok success.

Good video

"Some things are a must: you will not go viral without the lyrics written on the screen. It's a funny thing, but lyrics have never been more important than now.

"It has to be lit really well. Face is key -- you've got to show your face. You can't be off by a tree.

"In the swiping culture, the first milliseconds matter. You can't be fumbling with a guitar.

"People often do it by speaking first: 'Here's a song about Nelson Mandela...' or whatever. That's better than if you just start singing a song about Nelson Mandela."

Don't get fancy, he adds: "TikTok doesn't reward high production costs. Me sitting here in my studio singing a song is no different than if I had 50 oiled-up dancers in a football stadium."

Simple hooks

"There's a crudeness to my piano style. It's gentle, melodic and rhythmic, but quite blocky -- not up and down the keys like a virtuoso. That means it edits nicely for TikTok videos.

"They're hooky lines, which is important because you only get 15 seconds (the most common time for TikToks). Plus, I've got a pleasant, inoffensive voice -- you're not going to throw up in your tea if you hear it.

"TikTok is a great leveller. Anyone can do it. Maybe you've got two chords on the guitar. You can put it on TikTok and millions of people can find it."

Ignore the easy money

"When one of my songs goes viral, the labels rush in and they are absolutely praying that I'm 22 and haven't got a clue what's going on and will take £20,000 (around $25,000) for the rights.

"I tell them: 'I know exactly how much these songs are going to be worth so if you want to start talking, fine, but it's going to be in the many millions.'

"As soon as they realise I know even a handful of things about how this business works, they disappear.

"There's still a place for record labels, they'll be fine. But if you're doing well as an independent artist and you're slightly good at organisation, you don't need them.

"A friend had 200 million streams, but unfortunately he was with a major label and he's yet to see a penny from it. That should have been close to a million quid. It's unbelievable what they get away with it.

You can't force it

"I've seen artists of significant calibre who write a whole album that they think will be perfect for TikTok and it's totally flopped.

"It doesn't work for an artist to say, 'My song deserves to be viral'. Sixty thousand songs are released every day -- it's not for them to decide, it's for the listener.

"The songs that have shot off for me, I haven't said: 'I want these songs to do well, I'm going to make a nice campaign and a special video where I wear a gold suit in a fancy studio.'

"I've done nothing. The songs are out in the world, people I don't know have used them. You can't control it."

But you can connect

"With TikTok, you know people are listening but they might not know who you are. You have to connect to them, and say: 'I'm the one who did that song, come over here for a bit.' Connect your face to the sound.

"There's a lot of moaning pop stars at the moment, saying: 'Oh no, I'm not a content creator, I'm a musician, I couldn't possibly make a video explaining what I do.' But really it's not that hard to make the occasional video!"