A NSW musician who penned a protest song in the wake of the Newtown school massacre in the United States has struck a chord with more than 170,000 listeners on YouTube.

Sammy Baker took just 12 hours to write, record, mix and master the song after reading newspaper accounts of the December 14 tragedy.

He called the song How Many More and posted the video on YouTube about midnight on December 19.

"I didn't eat or anything that whole day because I was so focused on it," said Baker, who works in the audio-visual production industry.

"It all just flowed out. The next day I slept."

When he woke, he saw the clip was receiving unusual attention.

About 80,000 people watched it in the first three days and by yesterday views had surpassed 172,000.

"I thought it was just going to be Facebook friends looking at it, so I was really surprised," the 21-year-old said.

The video shows Baker singing to the camera and playing his guitar against an all-black background. Later the footage is interspersed with black-and-white photographs of the 28 victims of Sandy Hook Elementary, and colour stills taken in Newtown in the aftermath of the shootings.

The song calls for tighter gun control as an answer to regular mass shootings in the US and is directed to President Barack Obama, who Baker accuses of "tell[ing] us something must be done but you wait for the next one instead".

It references the gunman, Adam Lanza, whose "mum bought these guns and bullets, approved by the NFA. A crazed young man with a gun in his hand walkin' down an empty hallway".

"This all feels so familiar, I've seen this all before," he sings. "Blood and tears and bodies; piled up on the cold, cold floor."

Baker said he initially dismissed the shooting as "another massacre" but was compelled to engage with the tragedy when he learnt most of the victims were children.

Baker owns guns - he inherited eight antique guns collected by his grandfather.

He believes it is possible the events in Newtown will result in change.

"Here in Australia it's a massive process to get a gun," he said. "We have police come around all the time to make sure bullets are in a separate place.

"In America you don't need to have a reason - anyone can buy a gun over there."