Liam McGrandles shared a video of himself and the music icon covering Irish ballad Grace on Tuesday, which has since been viewed 33,000 times.
The 38-year-old struck up a friendship with the star through their shared love of Celtic, and the duo previously sang together at a Celtic FC Foundation gala dinner in Manhattan in 2019.
However, it was his wife, Fiona, who helped to bring about their latest duet.
Explaining how Sir Rod got on board, Liam said: “It was my wife’s suggestion.
“She suggested it to him and he was well up for it and said it was a great idea.
“He emailed me a couple of weeks ago. He’s had some recording and adverts to do so it’s been a couple of weeks in the making. Rod recorded it in his home down south.
“I’m absolutely delighted. It’s sounding brilliant!
“The feedback has been amazing and all positive so far. Everybody seems to be loving it.
“Rod keeps in touch all the time, just talking about music and Celtic.”
The pair’s friendship is clear to see on screen, as Sir Rod says at the start of the clip: “Hi Liam, we’ve just finished the last vocal on the new album and you’ve been waiting for this so here we go.”
At the end, the rocker jokes: “That wasn’t a good key for me, Liam, you know that!
“All the best, mate.”
Given the response he’s received to the footage, Liam is keeping the door open for future duets.
He said: “Rod’s the kind of guy who would be up for it again, but I’m not the person to go and ask him for anything.
“He wants to go and have a night out when things are back to normal. We were meant to go out after the Celtic and Rangers game before the first lockdown. He just seems to like me!
“Throughout the lockdowns I’ve done fundraisers for the Celtic Foundation and a couple of gigs for Celtic’s virtual matchday pass.
“I’m just hoping it continues when gigs come back.”