But little did he know there's a surprise waiting for him in the audience.
The 16 year old school boy from Surrey started playing piano aged 7 and has been busking since the age of 13.
He said his dad, who works overseas 9 months of the year, is his biggest fan but couldn't attend the audition.
However Reuben got a shock when his dad popped up in the audience to surprise him.
"He's gone to bits," said Amanda Holden as Reuben was left emotional by the sight of his father in the crowd.
Reuben went on to perform his own song called Lifeline, explaining it was an apology song to his girlfriend who previously dumped him.
After Reuben's performance, Simon Cowell said: "Good for you. That was a great audition Ruben, you've come on and been authentic, be original. I really, really like the song, You've got talent."
David Walliams added: "What a talented young man you are. Incredible to write such a beautiful song at your tender age to sing it so beautifully."
And Alesha Dixon said: "I've so much admiration for you, you're up there bearing your heart and soul and that makes you really vulnerable... I'm sure your dad was proud."
With four yeses, Reuben sailed through to the next round of the competition.
Britain's Got Talent 2017 is back Saturday night at 8PM on ITV with More Talent straight after on ITV2 from 9:20PM.