As I compiled this list of musical scenes written or improvised by the actors who performed them, I quickly realized that I could never cover everything. The amount of music written by the actors in Christopher Guest films alone would more than double the size of this article. So I tried to limit myself to scenes and movies that I'd be able to give some fun insight on.
I literally got goosebumps rewatching some of these musical scenes. I hope you're inspired to give some of these movies a whirl in the DVD/Blu-ray player afterwards with a new sense of appreciation for the work that went into these musical moments.
The Return of The King - "The Edge of Night"
Though the lyrics are straight out of the J.R.R Tolkien novel, the tune for "The Edge of Night" was written by actor Billy Boyd. After seeing Boyd knock out some tunes at a karaoke bar, writer/producer Philippa Boyens was struck with the beautiful quality of his voice. Remembering that Denethor asks Pippin to sing him a song in the book, she presented the lyrics to Boyd and asked if he could come up with a tune for it. Boyd wrote the lullaby-like melody with the idea that this was a song that Hobbit mothers would sing to their children.
On the DVD/Blu-ray extras, you can hear the amazingly pure on-set audio for the scene. The final version however, used for the soundtrack and film, was recorded at the famous Abbey Road studio.
Much like Billy Boyd, Viggo Mortensen was tasked with taking J.R.R. Tolkien's words and transforming them into song. Though "Aragorn's Coronation" song isn't as memorable as Pippin's, Mortensen had the more daunting assignment, seeing as how the lyrics were in Elvish. This video provides the English translation for the song. It's quite touching.
School of Rock - "Math Is a Wonderful Thing"
The movie itself is based off of writer Mike White's experience living next to Jack Black, who would often roam the apartment halls naked, blasting classic rock tunes, many of which ended up being used in the film. Black does much of his own guitar playing in the movie, but he left the "heavy lifting" of guitar solos to studio musicians. The guitar solos were so difficult for Black that when he and the children featured in the movie (who also can really play their instruments) played live during their publicity tour for the film, he would simply sing the guitar solos. This "guitar scatting" technique is also used by Black for many Tenacious D songs in place of guitar solos.
Additional Note: All of the songs that Jack Black wrote for the film, "Math is a Wonderful Thing", "In The End of Time"(the song the band intended to play for the talent show) and "Step Off", are only ever played in scenes that take place in the classroom. In the DVD commentary, Mike White revealed that he had originally envisioned the entire movie as a musical.
The Wedding Singer - "Somebody Kill Me"
Along with the original songs Adam Sandler co-wrote with the film's screenwriter Tim Herlihy, there was so much music in this film that 2 different soundtracks were released; The Wedding Singer Volume 1, and The Wedding Singer Volume 2. In the movie, many of the songs were sung by cast members, but the original artists' versions of the songs are featured on the soundtracks. The only exceptions are Ellen Dow's rapping granny version of Sugar Hill Gang's "Rapper's Delight," and The Presidents of the United States of America's cover of "Video Killed The Radio Star," which was originally performed by The Buggles.
Additional Note: In April of 2006 a Musical based on the film debuted on Broadway, and ran until the end of the year, earning Tony Award nominations for Best Musical, Actor, Book, and Score.
"Grow Old With You"
The Hangover - "Stu's Song"
The cast and crew of The Hangover spent close to three weeks on the hotel suite set. Between takes Ed Helms would fool around on the piano that was part of the set, and try to make the cast and crew laugh. One day, director Todd Phillips suggested to Helms that he write a song about the tiger, which would serve as a breath in the narrative. Within that day, Helms wrote it, and after he and Phillips "tinkered" with it a bit, they shot the scene.
Additional Note: The song playing during the freeway tuxedo delivery scene towards the end of the film is performed by the band Revolution Mother. The tuxedo delivery guy is Mike Vallely, famous pro skateboarder and lead singer of Revolution Mother. Vallely also appears in the intervention scene in The Hangover Part III.
Step Brothers - "Boats n' Hoes"
Step Brothers had quite the original score by Jon Brion, but it also featured some classic tunes. The cast did hilarious renditions of Andrea Bocelli's "Con Te Partiro (Time To Say Goodbye)" and Guns 'N Roses' "Sweet Child o' Mine." We were also reminded that "Ice Ice Baby" really was a great song. But it's the Will Ferrell and John C. Reilly penned rap "Boats 'N Hoes" that got stuck in our heads.
Slackers - "Ethan's Song"
Most people are familiar with Jason Schwartzman from his roles with frequent collaborator Wes Anderson. A lesser number know that he was the drummer for Phantom Planet, and the chief songwriter behind their unofficial west coast anthem "California," which was used as the theme song for The O.C. And sadly, an even smaller fraction know Schwartzman under his moniker Coconut Records.
The movie Slackers ends with Schwartzman playing this awesome Beatles-esque number that he wrote. Despite it being mostly comedic, the song gives The Police's "Every Breath You Take" a run for its money in both catchiness and utterly creepy stalker-themed lyrics.
Additional Note: The single "Hey Now Girl," performed by Schwartzman's band Phantom Planet, was used in trailers for the film.
Empire Records - "Sugar High"
Actor/musician Coyote Shivers played Berko in the film Empire Records, a movie which wasn't a commercial or critical success upon its release, but has since become a cult classic. Shivers wrote and performed the song "Sugar High" for the Beatles-inspired rooftop scene of the film, which features backing vocals and additional lyrics sung by Renee Zellweger. The soundtrack version doesn't include Zellweger's vocals and is played in a higher key.
Additional Note: During the filming of Empire Records, Coyote Shivers was married to Bebe Buell, which made his co-star Liv Tyler his step-daughter.
Nacho Libre - "Singing at the Party"
The musical scenes in Nacho Libre have Jack Black's signature stylings all over them, so it's no surprise that he wrote them. There was some behind the scenes drama surrounding the film's original score though. Director Jared Hess initially commissioned Beck to score the film. However, fearing that Beck's music didn't fit the movie, Paramount hired composer Danny Elfman to replace him.
Hess only used 2/3 of Elfman's full score in the movie, but representatives for Elfman wanted him to receive sole credit for the score. Hess would not allow the studio to remove Beck from the credits, and a deal was eventually worked out where both musicians were given credit for their respective parts of the score.
Additional Note: Along with writing the title character's musical numbers, Jack Black performed many of his own stunts. One of the stunts, which called for Black to jump from the wrestling ring, went wrong. Black struck his head on a chair and walked away with a black eye and a laceration that required stitches.
Forgetting Sarah Marshall - "Dracula's Lament"
Jason Segel not only wrote the script for Forgetting Sarah Marshall, which he based partially on his real-life break up with his Freaks & Geeks co-star Linda Cardellini, but he also wrote much of the music that appears in the film. Segel co-wrote the Infant Sorrow songs performed by Russell Brand, as well as the Dracula musical songs. That part of the script is also true to life, based on Segel's own attempts early on in his career to adapt Dracula for puppets.
Additional Note: Segel's character Peter plays part of The Muppet Show theme song in a scene in the movie. Segel would go on to star in 2011's The Muppets, which he co-wrote with Forgetting Sarah Marshall director Nicholas Stoller.
8 Mile (2002)
Eminem wrote the single "Lose Yourself" in-between takes while filming 8-Mile. The track is still the rapper's highest selling song. The piece of paper his character Jimmy is writing on in the movie is the real sheet that "Lose Yourself" was written on. That piece of paper later sold for $10,000 in an eBay auction. The song, however, is never actually performed in the movie -- with Eminem's references to 8-Mile actor Mekhi Phifer, it would have been confusing had it been.
"Lose Yourself" may have been the soundtrack's breakout hit, but it's the film's climactic rap battle that gave audiences the chills.
The Princess Diaries - "The Blueside"
Though Robert Schwartzman wouldn't hit big in the acting world like his big brother Jason or his cousin Nic Cage, he and his band Rooney would hit the music charts with their infectious debut single "The Blueside." Robert and the band can be seen playing an early version of the track in the scene below. Robert's character was written out of the sequel, and the explanation for his absence was true to life: He was touring around the world with his rock band.
Writer/director John Carney enlisted his long time friend and former Frames bandmate Glen Hansard to write the songs for his movie. Hansard recommended his friend Marketa Irglova for the female lead as it called for an Eastern European, and she began contributing songs for the film.The lead role was originally meant for Cillian Murphy who dropped out, fearing that he would not be able to sing Hansard's octave jumping compositions. After coming to the conclusion that he'd be "much better off having musicians who can half act than actors who can half sing," Carney offered the role to Hansard. The song "Falling Slowly" would earn Hansard and Irglova an Academy Award for Best Original Song. After being cut off by the orchestra before a commercial, Irglova's touching acceptance speech became one of the most memorable and talked about moments of the awards ceremony that year.
Additional Note: After the film, Hansard and Irglova began a real life romance, the start and end of which is captured in the duo's self titled documentary The Swell Season. A musical adaptation of the film opened in March of 2012 on Broadway. It was nominated for 11 Tony Awards, and walked away with 8, including Best Musical.
Magic Mike - "Ladies of Tampa"
Matthew McConaughey didn't have a stripping scene in the original script for Magic Mike. Not only did the actor want one, but he had the idea of first serenading the women from the stage. Along with music supervisor Frankie Pine and McConaughey’s guitar coach Martin Blasick, McConaughey penned "Ladies of Tampa" in about three hours at his hotel room.
This is Spinal Tap (1986)
The first of its kind, this mockumentary was so convincing that early home video versions of it contained a disclaimer at the end of the film informing audiences that the band and events weren't real. In Norway, the title of the movie and cover art were changed to resemble the parody movie Airplane! and a disclaimer was shown throughout the film. The improvisation between all of the performers is part of what made it feel so real, but what really made the movie feel authentic was the fact that Christopher Guest, Michael McKean, and Harry Shearer wrote and performed all of their own music. They have toured the world for decades now both in and out of character as Spinal Tap.
Additional Note: Guest, McKean, and Shearer also wrote and performed as The Folksmen in 2003's A Mighty Wind.
A Mighty Wind - "Eat at Joe's"
Ferris Bueller's Day Off (1986)
With how "good" Matthew Broderick's clarinet playing is in this scene, it's not hard to imagine that it was improvised. Along with the hilarious line, "Never had ONE lesson!", it's interesting to note that the entire scene itself was improvised. The scene was shot after someone spotted the instrument as part of Ferris' bedroom set and Broderick claimed that he could play it... which he couldn't. The keyboard coughing scene was also improvised by Broderick.
Additional Note: Despite being a very musical driven film, writer/director John Hughes felt that the songs used were too uneven and didn't flow well together. There was never a soundtrack released for the movie.
The Hangover - "Three Best Friends"
Quite a few jokes were lifted right from Zach Galifianakis' stand up routine, including; Alan joking that he isn't allowed near schools or Chuck E. Cheese, and Ken Jeong referring to him as "Fat Jesus." The "Three Best Friends" scene also comes straight from Galifianakis' noggin. He and Ed Helms improvised these two back to back numbers, and in this extended version of the scene we get to see a lot more of both songs.
Additional Note: After seeing Galifianakis lip sync in the video for Fiona Apple's "Not About Love," Kanye West commissioned the comedian to do the same for an alternate video for his single "Can't Tell Me Nothing," which is also featured in The Hangover.
A Clockwork Orange - "Singing in the Rain"
The audio of Malcolm McDowell singing a rendition of "Singing in the Rain" wasn't originally intended to be used. Director Stanley Kubrick liked it so much that he decided to keep it in, even though attaining the rights to use it in a scene that graphically depicted rape would of course be difficult.
Once - "Broken Hearted Hoover Fixer Sucker Guy"
This scene was a spontaneous moment from Glen Hansard that was caught on film, and Marketa Irglova's reactions to the impromptu lyrics were genuine. Director John Carney liked it so much that he used it in the final cut of the movie, much to the amusement of Hansard.
Though not necessarily written or improvised the actors, here are some musical scenes that were directly inspired by them.
Juno - "Anyone Else But You"
Writer/director Jason Reitman had originally intended for the character Juno to be more into glam rock. For the sake of giving the movie a more authentic feel, he decided to put Juno's musical tastes in the hands of actress Ellen Page instead.
"I asked Ellen Page before we started shooting, ‘What do you think Juno listens to?’ And she said [‘The Moldy Peaches.'] She went on my computer, played the songs, and I fell in love with it. [Screenwriter] Diablo [Cody] and I discussed putting a Moldy Peaches song in it where the characters would sing to each other. I got in touch with Kimya Dawson of The Moldy Peaches, and she started sending me her work, which was beautiful, and that became a lot of the soundtrack."
Additional Note: Ellen Page and Michael Cera both already knew how to play the guitar and both actors are originally from Canada. Cera would go on to play the bass guitar in Nick and Norah's Infinite Playlist and Scott Pilgrim vs. The World. Cera was so much more advanced than his Scott Pilgrim cast mates that he reportedly had to simplify his playing so as to not outshine them.
500 Days of Summer - "Sugar Town"
We all know Zooey Deschanel can sing. She's proved that in almost every one of her movies. When we interviewed her for this film, she actually said that she kinda hates having to sing in movies, because often times people criticize it even though it's not how she would sing, but how she felt the character would sing. For the karaoke bar scene though, director Marc Webb let Deschanel choose her own number. She chose to do Nancy Sinatra's "Sugar Town."
Super 8 - "My Sharona"
After seeing the young actors singing a current song between takes for other scenes, writer/director J.J. Abrams reshot this scene in order to inject more "fun" into it. He gave the actors the song lyrics to The Knack's "My Sharona" in the morning, and they performed it that night. None of the actors had ever heard the song, and really didn't care for it. "My Sharona" debuted in 1979, the same year that the movie takes place.
Bonus: Sitting next to producer Steven Spielberg, J.J. Abrams gives an in depth explanation of the scene, and the frantic scramble to get it set up and shot before looming rain clouds began to pour.
Kazaam - "We Genie"
It's bad enough that Shaquille O'Neal did his own acting in Kazaam, but it was just unfortunate for a young Francis Capra that Shaq did his own rapping too. Despite his lack of cred, Shaq is a platinum selling rapper. Shaq was an outstanding basketball player who couldn't shoot, and a successful rapper who couldn't rhyme. Those are two things that sound suspiciously like wishes granted by a genie.