The copyright infringement verdict against pop star Katy Perry's hit single Dark Horse might appear as a victory for the underdog artist, but it's also raising concerns about what constitutes theft versus inspiration in the music industry.

"I think it can be a very difficult line to draw," said Seattle-based intellectual property lawyer J. Michael Keyes. "It's not really clear what's an homage or inspiration, and what's illicit copying. I think it's hard to know going into it."

On Thursday, a jury ordered that Perry, her collaborators and record label must pay $2.78 million US after concluding her popular 2013 song copied a section of the 2007 Christian rap song, Joyful Noise.

Perry and her team insisted they'd never heard the track. But the artist behind Joyful Noise, once known as Flame, argued the song was viewed more than two million times on YouTube and was nominated for a Grammy Award. Perry's strong Christian upbringing and pastor parents were also flagged as possible reasons she might have been familiar with it.

Texas-based composer Paul Croteau, who's done work for shows like The Young and the Restless, Keeping Up With The Kardashians and American Greed, says the decision has ramifications for many artists.

Listen to Dark Horse and Joyful Noise below.

"I now have to alter how I work. I have to do more research and cross my fingers and wonder, 'Did I unintentionally copy something I've never heard?'" he said. "It alters the way we think and it really blows up the creative process."

Croteau is one of many who have taken to social media to argue the two songs might sound similar, but not enough to warrant the significant payout. He posted a graphic online to illustrate the minor discrepancies which he says make a major difference.

"The drumbeats are completely different," said Croteau. "The songs are in different keys and different tempos. The verdict scares me because .... that can lead to massive amounts of lawsuits in the future."

Composer Paul Croteau took to social media to illustrate the musical differences between Katy Perry's Dark Horse and Flame's Joyful Noise. (Paul Croteau/yopauliemusic.com )

Keyes, who has both a legal and musical background and has written extensively on the issue of copyright, believes the "jury got it right" under U.S. law, but that's also part of the problem.

Dark Horse was cited for a short series of beats which play throughout the song deemed to be too similar to the ones in Joyful Noise — a huge blow to artists and record companies.

"If you can be liable for allegedly copying a three-note phrase, I think that really dampens the creative output of artists," said Keyes.

Keyes is a proponent of the industry moving toward a "large, compulsory licence system" in which anyone has the right to access released music as long as they pay a fee.

He admits there's a "fair amount of pushback" on the idea but in this age of streaming and technology, he argues copyright issues will otherwise continue to pop up more frequently.

Several high-profile artists have recently learned that the hard way.

Blurred Lines

The Dark Horse verdict follows a string of recent music copyright cases which have muddied the waters when it comes to inspiration versus plagiarism.

Musicians Robin Thicke and Pharrell Williams were ordered to pay approximately $5 million US last year after an appeals court upheld a 2015 verdict stating that their pop song Blurred Lines — the biggest hit of 2013 — copied Marvin Gaye's 1977 song Got To Give It Up.

Gaye's family had accused the singers of copyright infringement. Further appeals to challenge the verdict continue.

Listen to the similarities between Blurred Lines and Got To Give It Up below

Taylor Swift, Sam Smith give credits

While Thicke and Williams continue to appeal, other artists have opted to pre-empt a potential legal battle by giving credit where credit is due.

Taylor Swift credited the writers behind the catchy single I'm Too Sexy on her 2017 release Look What You Made Me Do, which interpolates the melody of the 1991 one-hit wonder.

British crooner Sam Smith settled a dispute involving his Grammy-winning song Stay With Me, which was targeted for copyright infringement by the writers of Tom Petty and the Heartbreakers' 1989 rock classic I Won't Back Down.

Petty and co-writer Jeff Lynne were given songwriting credits on Smith's 2014 tune and a portion of the royalties, however, Smith maintains he had never heard I Won't Back Down before he wrote his own megahit.

Listen to Stay With Me and I Won't Back Down below.

Ed Sheeran will have jury Thinking Out Loud

British singer-songwriter Ed Sheeran settled a suit against his song Photograph, alleged to be a "note-for-note copying" of the song Amazing, recorded by Matt Cardle, the winner of the British version of The X Factor in 2010.

Sheeran also gave additional songwriting credits to the writing team behind TLC's 1999 R&B hit No Scrubs on his No. 1 track Shape of You — the best performing song of 2017 — after similarities were noted between the two songs following its release.

But Sheeran wasn't able to dodge every accusation of duplication. He's currently facing a $100-million US lawsuit alleging his 2014 hit track Thinking Out Loud copied in large part Gaye's 1973 classic Let's Get It On.

Keyes says music has always relied on previous work to create new sounds and genres.

"It thrives by people being able to hear different musical ideas and being able to incorporate that into their music to create a new work," said Keyes. "We should get back to that premise."