It is a scene touching enough to make grown men bawl their hearts out - the sight of a man singing to his wife on her deathbed to profess his undying love.
The 3 1/2-minute video of the incident, which was filmed by the elderly couple's granddaughter Erin Solari and posted by her on Facebook on Sept 12, has gone viral.
It has been viewed more than 3.2 million times.
The New Orleans-based Ms Solari shared that her grandmother Laura, 93, first sang the classic tune You'll Never Know to her grandfather Howard, 92, when he left to fight in World War II.
Laura's attempt to croon the song one last time was reciprocated by her loving husband, as he tenderly stroked her face.
A friend of the couple, Joy, told littlethings.com that the video had brought up "many emotions" in her.
"It has somehow captured in just a few minutes an entire lifetime between two people," she said.
"They have been each other's witness for 73 years, growing up and growing old together, holding onto some memories that only the two of them share, each of them being proof to the other that those memories are real."
Comments left on the post by netizens thanked Ms Solari for sharing the moving moment.
"They sure don't make love like this anymore," wrote one. Another summed it up best: "I don't really have words enough to express..."
Listen to the original song, sung by US singer Alice Faye in the 1943 film Hello, below.