New York (CNN) Musician Ed Sheeran looked visibly frustrated on the stage Monday as he continued his testimony in the second week of his copyright infringement lawsuit over whether his single “Thinking Out Loud” copied Marvin Gaye’s classic “Let’s Get It On.”
Sheeran said he found the allegations in the case “really insulting”. At some point, the musician said: “I will not swear.”
He also disputed the testimony of Alexander Stewart, the plaintiffs’ expert witness. Sheeran claimed that Stewart altered elements of “thinking out loud” in his analysis to make his point.
Stewart claimed during the trial last week that the chords Sheeran played in the first 24 seconds of his song were “nearly identical” to “Let’s Get It On.”
Sheeran said that the chords on “Thinking Out Loud” are a “common twist”, and that similar chords are used in many songs.
To prove it, he played the chords from “Thinking Out Loud” while singing several different songs by other artists, including “Tupelo Honey” and “Crazy Love.” He testified that he did not transcribe those songs when he wrote “Thinking Out Loud”.
On Thursday, Sheeran played the opening line of “Thinking Out Loud” in an attempt to disprove Stewart’s testimony.
Later on Monday, Amy Wadge, who co-wrote “Thinking Out Loud” with Sheeran, testified that she used “the same chord progression” on an earlier song.
Pete Wiley released “Better Than Me” before Wadge and Sheeran wrote “Thinking Out Loud” in 2014.
Sheeran previously testified that Wadge came up with the basic chord progression in the first part of the song.
She said that Wadge has not been formally taught how to play the guitar and because her skill level is “very basic”, she has to rely on the building blocks.
“I was playing some simple chords that I knew how to play,” Wudge said on the stand, adding that she has used similar chords on other songs.
She said it was “not possible” that she could have violated another song, whether intentionally or not.
Also Monday, a music expert testified for the defense that he saw “no musical evidence” that Ed Sheeran and his partner had transcribed “Let’s Get It On” when writing “Thinking Out Loud.”
“The authors of Thinking Out Loud didn’t imitate Let’s Get It On,” expert Lawrence Ferrara said on the stand.
Ferrara said the chord progression was “in common use” before “Let’s Get It On”, and the harmonic rhythm is “normal”. He said the melodies in question are “wildly different” and have only “chippy similarities”.
Ferrara is expected to continue his testimony on Tuesday.
Sheeran is accused of copying “Let’s Get It” by the heirs of Ed Townsend, who co-wrote the 1973 song with Gaye. Townsend’s daughter Katherine Townsend Griffin, her sister Helen MacDonald, and the estate of his ex-wife Sherigal Townsend are the plaintiffs included in the “Thinking Out Loud” case.
Jay died in 1984 and Townsend passed in 2003.
When asked at the stand Monday what he would do if the plaintiffs won the case and owned the chord progression, Sheeran said, “If that happens, I’m done.”
CNN’s Chloe Melas contributed to this report.