Sam Smith claims any likeness was "a complete coincidence." Brad Barket/Getty Images for iHeartMedia If you've recently heard Sam Smith's hit song "Stay With Me" and thought, "Hm, this sounds kind of like Tom Petty's 'I Won't Back Down,'" well, you're not the only one.

After "Stay With Me" became the 22-year-old British singer's most successful single to date (it peaked at No. 1 on the UK Singles Chart and reached No. 2 on the US Billboard Hot 100), Petty and his cosongwriter Jeff Lynne took note of the ballad's likeness to their 1989 hit.

The two parties settled out of court this past October that the two songs are so much alike that Smith now pays Petty royalties on the track — specifically, a 12.5% credit, according to The Sun.

Tom Petty will receive 12.5% of the song's profits. Allen Berezovsky/WireImage via Getty Images

Jeff Lynne and Tom Petty were also added as cowriters on "Stay with Me" after Smith's lawyers settled the suit with Petty, despite the Brit claiming any likeness was "a complete coincidence."

Sam Smith's rep explained the situation in a statement to USA Today:

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. 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.

Michael Harrington, a professional musicologist who specializes in federal copyright matters, agreed that the two songs sounded awfully similar.

Harrington explained to USA Today: "It got to the chorus, and I just started smiling ... That's pretty close, just the slightest differences. Especially compared to what's in court these days, this one is really solid."

According to Harrington, the two songs have a sequence of almost identical phrases in Smith's chorus and Petty's verses that made a successful claim of copyright infringement likely.

A post on Medium shows the musical similarities between the two:

Here are the two tunes; the chorus of "Stay With Me" and the verse of "I Won’t Back Down" (transposed into the same key to make the comparison easier). medium.com/@edrex_ Check out the two songs and judge for yourselves below:

Or just listen to the lyrics below:

"Stay With Me" is nominated for a Grammy for record of the year, song of the year, and best pop solo performance. As of December 2014, the song had sold six million copies, becoming one of the best-selling singles worldwide.

