Sam Smith exults in the press room backstage at the Grammy Awards. (Frederic J. Brown/Agence France-Presse via Getty Images)

“I’m having a really, really, really good night,” Sam Smith said during the Grammys, and there was no fact-check necessary.

On Sunday’s prime-time CBS telecast, the ascendant blue-eyed British soul singer performed a duet with Mary J. Blige and heard his name called over and over from the stage. He collected four gramophone statues, including two of the biggest: Song of the Year and Record of the Year, both for the pleading anthem “Stay With Me.”

“This is the best night of my life,” Smith said after Stevie Wonder read his name (in braille) and Jamie Foxx handed the 22-year-old upstart the Record of the Year award. By that point, in his previous speeches, Smith had already thanked “my amazing label,” “my amazing management,” “Mum and Dad,” the Recording Academy and his producer.

In accepting Record of the Year, he said, “Dear Lord, thank you so much!”

And then, he thanked one more person. But it wasn’t the man whose famous name was on more than a few people’s minds, given recent headlines such as this one: “Sam Smith to pay Tom Petty royalties for basically writing the same song.”

Here, instead, is what Smith said in his last onstage comments of his really, really, really good night: “I want to thank the man who this record is about, who I fell in love with last year. Thank you so much for breaking my heart, ’cause you got me four Grammys.”

The specter of Tom Petty seemed to haunt the telecast: Every time Smith was mentioned as a nominee, the chorus of “Stay With Me” came tumbling out of the television. And it’s that song’s chorus that has become problematic for Smith.

Tom Petty in 2014. (Mario Anzuoni/Reuters file)

As the Sun first reported last month, Smith’s publisher settled a copyright dispute with Petty’s publisher in October over similarities between “Stay With Me” and Petty’s 1989 single, “I Won’t Back Down.”

“Recently the publishers for the song ‘I Won’t Back Down,’ written by Tom Petty and Jeff Lynne, contacted the publishers for ‘Stay With Me,’ written by Sam Smith, James Napier and William Phillips, about similarities heard in the melodies of the choruses of the two compositions,” Smith’s representatives said in a statement. “Not previously familiar with the 1989 Petty/Lynne song, the writers of ‘Stay With Me’ listened to ‘I Won’t Back Down’ and acknowledged the similarity.

“Although the likeness was a complete coincidence, all involved came to an immediate and amicable agreement in which Tom Petty and Jeff Lynne are now credited as co-writers of ‘Stay With Me’ along with Sam Smith, James Napier and William Phillips.”

As part of the settlement, the Sun reported, Petty and Lynne were awarded a 12.5 percent stake in Smith’s song.

But Petty and Lynne (who actually performed on Sunday night’s telecast, reviving the old Electric Light Orchestra) were not eligible for shares of Smith’s Grammys, the Recording Academy’s senior vice president of awards said before the ceremony.

“Since Lynne and Petty did not do any new writing for this work, we are considering their original work to have been interpolated,” Bill Freimuth said, according to the Wall Street Journal. “Lynne and Petty will not be considered nominees nor will they be considered GRAMMY recipients, should the song win. Rather, they would be given certificates to honor their participation in the work, just as any other writers of sampled or interpolated work.”

Jeff Lynne’s Grammy moment. (John Shearer/Invision/AP)

Petty, it’s worth noting, has never won a Grammy for Song of the Year or Record of the Year. (The former is for songwriting, the latter is for the performance and production of a song and really should have been renamed Single of the Year or Track of the Year ages ago.)

In fact, Smith’s debut Grammy haul surpassed Petty’s for his entire career: Smith has four Grammys, and Petty has won a three in his lifetime. (He does have that Rock and Roll Hall of Fame thing going for him, though.)

Smith told “CBC News Now” last week that he wasn’t familiar with “I Won’t Back Down” and that the similarities were coincidental.

“It was a complete accident,” he said. “I am 22 years old. . . . I’ve never listened to that song.”

He added: “I just go into the studio, and ‘Stay With Me’ was me just writing a song about me sleeping with too many people, and wishing they would stay over. That was my mindset when I was writing that song, and I was very shocked to find out that the melody was similar, because again, I am 22 and I’ve never heard the song.”

Petty himself shrugged it off, saying in a statement that “I have never had any hard feelings toward Sam” and that “all my years of songwriting have shown me these things can happen. Most times you catch it before it gets out the studio door but in this case it got by.”

(Los Angeles Times via Newseum) (Los Angeles Times via Newseum)

In fact, as the Los Angeles Times noted, Petty has previously acknowledged “channeling” other people’s songs himself. In the “official and authorized” book, “Conversations with Tom Petty,” the musician was asked about the Grateful Dead’s “Built to Last,” which had the same title as en earlier Petty song.

“That happens sometimes,” Petty said. “You look up, and you think you’ve come up with something, and you realize somebody else has done it first. You try not to let it bug you. What bugs you the most is when you write something and then realize it’s somebody else’s song.

“That’ll happen to me two times a month. I’ll be working with something and then realize I’m channeling this melody from somewhere else, and then I have to abandon the idea. But there’s only so many words and so many notes, so sometimes you do cross somebody else’s territory.”

The book’s author, the Times noted, asked, “Have you found that as the years have gone by, you’re better at knowing when you’re using somebody else’s melody?”

Petty’s response: “Yeah. And when that happens, I just have to throw it away.”

Author: “Throw it away or change it?”

Petty: “Well, I just usually pitch it. And start over. Because if I change a note or two, it’s still going to be in my head that it’s that other song. So I think every songwriter must have that problem from time to time. You play something and you realize it’s Beethoven, or the Beatles.”

As Billboard reported last month, “Stay With Me” was “not the first time Petty’s sound has been mined — surreptitiously or otherwise — by an emerging artist.”

As the trade journal noted:

The Strokes’ first single, “Last Nite” — particularly the opening — is very similar to Petty’s “American Girl,” a resemblance that Petty acknowledged in a 2006 interview with Rolling Stone. “I saw an interview with them where they actually admitted it. That made me laugh out loud. I was like, ‘OK, good for you.’ It doesn’t bother me.” Petty is not listed as a songwriter on that hit, however.

And anyway, as The Post’s Geoff Edgers wrote recently, there is “a rich tradition of ripping off other musicians — and having to fess up later.”

Here is a comparison of “Stay With Me” and “I Won’t Back Down”:

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