Bing-Bong’s song from Inside Out. OK, so it isn’t much of a song (oddly enough, it sounds like something a little kid would write), but it’s certainly integral to the plot.
The Cantina music in the original Star Wars.
“Swinging on a Star” from Going My Way. And also “Going My Way,” although that one didn’t impress the record studio execs in the movie. But the royalties from “Swinging on a Star” saved the church.
“The Wizard of Speed and Time” from the movie of the same name.
“Babysitting Blues” from Adventures in Babysitting.
(Link goes to the music video version; the movie just showed them performing on stage).
“A Taste For Love” and “Dracula’s Lament” from Forgetting Sarah Marshall
Thanks for making me cry, you MONSTER!
Nobody gets out of here unless they sing the blues. Wow. Talk about a movie I hadn’t thought of in a long time!
I’m going to say Footloose from the 1980s movie. I don’t think the cast are supposed to be singing the song, but I’m pretty sure I caught a couple of them mouthing the words in one or two shots.
“Cold One” from Ricki and the Flash. Essentially, the lead character’s mea culpa to her family.
Not quite integral to the plot but … the gum jingle earworm. Please don’t shoot me.
Baa Baa Barbershop is a charming little interlude (with some plot importance) in Shaun the Sheep.
Would Galaxy Glue from The Incredible Shrinking Woman count?
The very forgettable movie Euro Trip contains the song Scotty doesn’t know sung by Matt Damon is his greatest cameo ever. A pity I can’t link youtube from work.
I wouldn’t consider O Brother, Where Art Thou? a traditional musical. But maybe I’m in the minority on this.
I’ll add Que Sera, Sera sung by Doris Day in Hitchcock’s The Man Who Knew Too Much. It was very integral to the plot. Also won the Academy Award for Best Original Song that year.
After further investigation, while I still wouldn’t consider O’ Brother Where Art Thou, a traditional musical, Man of Constant Sorrow was not an original song for the movie, but written in 1913, some 87 years before the movie was made.
I presume koeeoaddi’s response doesn’t refer to the underlined clause but the first phrase in DCnDC’s excerpted post: original and written for the movie. “Man of Constant Sorrow” isn’t original to the movie as it’s a traditional or folk song. Wiki entry on the song
While thinking of this category, you must remember this movie: Casablanca
“Children of Piraeus” from Never On Sunday
“Yea Ho Little Fish, Don’t Cry, Don’t Cry” from Captains Courageous
“Brave Sir Robin” from Monty Python and the Holy Grail
“Leaning” (or “Lean on Jesus,” Robert Mitchum and Lillian Gish), Night of the Hunter
“Dueling Banjos,” Deliverance