This is one of the songs that Keira Knightley sings in the movie Begin Again. She plays Greta, a singer-songwriter who decamps for New York with her boyfriend when he lands a deal with a major label. "The songs weren't finished until two days before I had to record them in the studio. I had singing lessons and sang lots of scales to figure out what my range was and to strengthen my voice," she told The Express.
"Greta's not meant to like performing so that was quite helpful, it was part of the character, which was good because, with nerves, you generally just have to get rid of them because that's what your job is as an actor."
"(What's So Funny 'Bout) Peace, Love, and Understanding" was written by Nick Lowe in 1974. The original version with his group Brinsley Schwarz was kind of somber, but Elvis Costello made it a classic with his 1978 uptempo take.