It was a simple ballad inspired by taking a picture of his beloved. But Ed Sheeran may be regretting ever picking up that camera, after settling a $20m (£16m) plagiarism lawsuit for the song Photograph. The singer was accused of copying “note-for-note” from a song called Amazing, released by the X Factor winner Matt Cardle five years ago. Songwriters Thomas Leonard and Martin Harrington sued Sheeran, accusing him of “unabashedly taking credit” for their work. The songwriters claimed the chorus of Photograph and Amazing shared 39 identical notes and that the similarities were “instantly recognizable to the ordinary observer”. “This copying is, in many instances, verbatim, note-for-note copying, makes up nearly one half of Photograph,” they said in a complaint lodged in the US in July.

Lawsuit filed by Ed Sheeran

It is the second plagiarism lawsuit taken out against Sheeran in recent months, with an another ongoing case accusing him of plagiarising the melody, harmony and composition of Marvin Gaye’s Let’s Get it On in his track Thinking Out Loud.

Dr Joe Bennett, a musicologist based at Boston Conservatory at Berklee who specialises in music copyright, said the Photograph case was straightforward. Melodically “there are so many similarities between these two particular works, it is hard to dispute that it was obviously plagiarized and I’m not surprised they settled”. Bennett said that for a plagiarism case to be successful, lawyers had to prove substantial similarity, access (that the defendant would have heard the song), and the originality of the melody that was allegedly plagiarized.

The blurred line case

The Blurred Lines case has gone to appeal and Siddell said he and many in the industry expected the verdict to be overturned because “melodically there’s very little similarity – it sounded the same so that was enough to convince a jury”.

He added: “The processes of deciding these things is different in American courts, where they use a jury, as opposed to the UK, where you get an informed and knowledgeable judge who decides.”

Dennis Collopy, a senior lecturer in the music industry at the University of Hertfordshire, said that in plagiarism cases it was important to acknowledge the narrow musical confines of what makes a hit song. His own research showed 25% of the No 1 singles in the US over the past 60 years were written in the chord of G.

“We celebrate the fact that successful songs tend to fit into quite a narrow band of melody and structure,” he said. “It has to be two minutes long, it has to be catchy and include the chord progressions we are familiar with. When it comes to pop music, it’s very hard to be completely original and successful at the same time.”