Trying to predict who will and won't become an international pop star is an impossible task. You have to take into account indefinable variables such as charisma, charm and personality, and hope that music fans can see what you're seeing. This is where social media and sites like YouTube and musical.ly have become invaluable for talent spotters over the last few years.

Away from the fevered expectations of Saturday night talent shows, YouTube allowed talents such as Justin Bieber and 5 Seconds of Summer to broadcast their songs - usually covers of established hits - on their own terms, building a following by word of mouth and proving to record companies that they have what it takes to make it on the global stage.

So, as seasoned YouTuber Charlie Puth prepares to be one of the first guests on the new BBC One music show Sounds Like Friday Night (7:30pm on Friday 27 October), here's a look at some of the most popular singing vloggers of 2017 - all hoping to be real life household names in 2018 and beyond.

1. Samantha Harvey

The power of a decent following on social media is evident in the No.48 chart success of Samantha Harvey's debut single Forgive Forget, which she released herself in July of this year. Samantha has over two million followers on Facebook, who have watched her cover versions of songs by Ed Sheeran, James Arthur and even Charlie Puth (vlogger covering vlogger), then willed her to success as she packed in her day job running a cleaning business and self-funded a trip to LA to record the song with producer/songwriter Jayson DeZuzio (Little Mix, Jason Derulo, Dua Lipa).

Looking back to her first upload, Samatha told the Ipswich Star: "I was so scared to post that first one of Sam Smith's Stay With Me, sat in my bathroom for the acoustics. Six months in it went viral. I never, ever, expected it."

2. Toby Randall

Toby Randall is 16, and like a lot of his peers, he has spent the last four years posting cover versions online. His hard work is truly paying off - recently, he was snapped up by JAY-Z's Roc Nation label, and last week released a debut single, Landslide, which begins with DJ Khaled yelling, "I introduce you to young Toby, young greatness, UK London massive bless up!" at the beginning.

He's actually from Northampton, and has gathered more than 750,000 subscribers on YouTube thanks to the mournful grain of his voice and his sombre treatments of big pop songs like Clean Bandit's Rockabye, his biggest hit to date at 2.9m views.

3. Twin Melody

This year has been the year not just of Ed Sheeran's Shape of You, but Despacito, which was already an enormous viral hit across Spanish-speaking countries before Justin Bieber released his own version in April. Which makes Spanish sisters Aitana and Paula Etxeberria particularly astute cover artists, as they had already put their version online in February.

Having been uploading their piano-and-two-voices duets since 2013 as Twin Melody, Aitana and Paula really hit viral paydirt towards the end of last year with their dance interpretation of Zay Hilfigerrr & Zayion McCall's Juju On Dat Beat. The figures speak for themselves: Despacito pulled in over 4.5m views, but Juju was watched by more than 31m people.

4. Jadyn Rylee

Not every would-be viral pop star is rushing to grab the latest chart hits for their covers. Canada's Jadyn Rylee is 12, and while she hopes to follow in the footsteps of her country's other great YouTube star, Justin Bieber, her choice of material is very different.

Jadyn specialises in classic rock, anything from Metallica to Dolly Parton. She even gave Simon & Garfunkel's Sounds of Silence a strident gothic makeover that is surprisingly powerful, despite her tender years. That cover - in which she was joined by the similarly youthful (and popular) drumming vlogger Sina - topped 6.4m views.

5. Macy Kate

Certain cover artists find themselves in the wonderful - if unorthodox - position of being really big online, really popular with live audiences, playing to huge crowds, but relatively unknown as crossover pop stars. Perhaps the biggest of these is J.Fla, the South Korean singer whose covers of worldwide pop hits have achieved as many as 100m views each.

Macy Kate is in a similar league, having worked up a strong online profile over the past few years, with recent hit covers of Rihanna's Work and Ariana Grande's Dangerous Woman sitting around the 5m views mark. Her version of Shape of You (easily the most popular cover song of the year) managed to stand out in a crowded field, with 3.9m views on YouTube, and possibly because of this decisive uptick in her viewing figures (and over 380,000 Facebook friends), she has just released a single, Property, to try and make that all-important final leap into the big leagues.

6. Talia Martinez

Talia, who is 26 and from Las Vegas, started posting songs early in 2012, mixing her own compositions - such as Mama and Feel That - with covers of her favourite songs, including plenty of Ed Sheeran selections.

Her most successful cover to date has been Despacito, which has over 4.5m views, with Ed Sheeran's Perfect and Zayn and Sia's Dusk Till Dawn (another very popular YouTube cover choice) rounding out her personal top three.

7. Allie Sherlock

It's the lesser-known Ed Sheeran song Supermarket Flowers that helped 12-year-old Allie Sherlock achieve online prominence, when a clip of her busking the song in Cork was uploaded and went viral, thanks in no small part to her exceptional voice.

One of the most interesting twists in Allie's story is that she has turned down several high-profile offers - including an appearance on Ellen DeGeneres's show in the US, because she's not at all sure she wants to be famous, or at least not yet. She told the Evening Echo she just likes the busking: "I don't want it to be a professional career but I'd like to do it, just as a hobby. I'd like to do childcare because my auntie owns a creche. I want to keep practising all the time and singing and so it's like a hobby really."

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