Nick Harvey’s father has dementia and had been hospitalized, so he hadn’t been to his son’s house in East Sussex, England, all year.

But on Sunday, Harvey invited his father for lunch. When he arrived, Paul Harvey, 79, went straight for the piano.

“It is like a magnet to him — he is MADE of music,” Nick Harvey said in a written interview with The Washington Post.

At his son’s piano, Paul Harvey, a former composer and concert pianist, played a classical piece first. Nick Harvey recorded it on his phone.

“I didn’t know how many more chances I’d get to capture him playing like that,” said Nick Harvey, who also is a composer and writes music for British television shows.

Then Nick Harvey asked his father to play “Where’s the Sunshine,” a piece Paul Harvey composed in the 1980s as music director of a British secondary school. Nick Harvey said that, like many of the other songs his father wrote for school productions, it could have “easily been good enough for the West End stage.”

Nick Harvey wasn’t sure his father would remember this one. It’s clear in the video Paul Harvey wasn’t sure about that, either.

In the video, he hesitates as he begins, then confidently and fluidly plays the composition he wrote decades earlier. His son posted it on Twitter. Within a day, it had been viewed more than 2 million times. Tens of thousands of people reacted with awe and admiration. Celebrities including James Corden and British singer Emeli Sandé retweeted it.

Nick Harvey included this note with the video:

“Dad has dementia. Sometimes he drifts into another world and I feel like I’m losing him. He is never more present, however, than when he plays the piano. He came to mine today and I asked him to play one of his compositions. He thought he wouldn’t be able to remember it.”

Some of the people who reacted to the video wrote that they remembered Paul Harvey and his compositions. Many others wrote that they were moved by his playing.

“What an utterly beautiful piece of music, made even more poignant by the sight of the ‘like’ counter rolling up as I listened, testifying to hundreds of others feeling as I did,” wrote one woman on Twitter.

“Oh, doll. That is so very lovely. Bless your dad. The next few years will be so hard but hopefully he will have moments like this to remind you all that he’s still here. Love to you all xx,” wrote another.

Nick Harvey said he’s “absolutely over the moon” for his father’s sudden celebrity.

He extended a thank-you from his father to his new fans and said his father is his “musical idol.”

“He deserves wider recognition,” Nick Harvey said. “He has more talent in his little finger than most people have in their whole body.”

He also found the original sheet music.

Nick Harvey said the past few days have been emotional for him, starting when he began the recording of his father playing “Where’s the Sunshine,” his now-viral song.

“Behind my phone, I was choking back tears. I knew it would be an incredible keepsake for the whole family,” he said.

In an interview with the Press Association news agency, Paul Harvey said he is happy his music is reaching masses of people, even at this late stage in his life, and even though he has dementia.

“I am very pleased that something I’ve written has had such an effect,” he said. “It’s come so late in life, it shows that it can happen at any time.”

Read more:

This woman has been on a three-year road trip documenting acts of kindness

I opened up about my stalker to a true crime podcast. Here’s why it helped me heal.

Little Free Pantries are like Little Free Libraries — but with food