Harvey said he started to play the piano because he found learning the music "satisfying".
He has performed at the care home where his mother works and on public pianos at railway stations.
"It is really nice when you get applause from people. It makes you feel like your performance has been accepted," he said.
Jen said he had not inherited his ability from her, joking that while she could play "Chopsticks", she would not describe herself as musical.
"He's taught himself off YouTube," she said.
"[He has] just decided 'Yes, that's what I want to play' and since then, he's on there for hours a day".
Jen said she was very proud of Harvey and keen to explore what his musical talent might mean for his future.
Previously he had been very interested in computers and design but she said his pivot to playing music was a surprise.
Harvey has just started lessons at formal lessons at The Norfolk Academy of Music.
His teacher Bekki Smith said Harvey was already playing at the top Grade Eight level.
Ms Smith said: "My first reaction was 'Wow, we've got something special here' and yes, playing to that standard after only a few months is rather amazing.
"He has brilliant dexterity for his age and his capability is amazing."
Ms Smith said she would be working with Harvey on filling in some of the gaps in his knowledge that came from learning online.
She said practice was key to progress like his.
"Harvey does at least two hours of practice a day and is very keen to learn which makes a huge difference from a lot of pupils that 'don't have the time' or can only play for 10 minutes a day.
"Sadly, a lot of pupils will find hours for social media but not for practice."
