To quote myself (post #10): punt, to another thread.
But I’m fuzzy on where to draw the line on *20th *century music. 21st century is a no-brainer – it’s out. (My thread, my rules. 
)
“Carmina Burana” was the first tune to pop into my head. For which I am forever grateful because it removed the horrible earworm I had for no reason today.
Kubrick was a master as using classical music. There’s also “The William Tell Overture” from A Clockwork Orange
I know you are talking about the “Lone Ranger” part of the overture, but he also used the first movement, as part of the scene where Alex is looking at the dreary river after being kicked out of prison and home. That was a very effective use of that haunting tune.
The use of the 9th symphony throughout the film was very well done.
Indeed, it was from watching this film as a teenager that I first was introduced to many of these classical pieces. I bought the soundtrack and then started listening to various other recordings of Rossini and Beethoven.
The use of 4’33" during the heist scene in Rififi was inspired.
*Beethoven’s 6th Symphony * from Solyent Green
*Beethoven’s 9th Symphony * from Help
The William Tell Overture from The Lone Ranger
The Merry Widow Waltz from The Merry Widow (I don’t remember which version)
Requiem was used for the monolith, and thus for the very beginning of the Stargate sequence. Atmospheres, also by Ligeti, was used for the rest.
The laughter and odd sounds during the hotel room scene came from Adventures by Ligeti, uncredited in the movie. I think Ligeti sued, because only excerpts were used. The original soundtrack didn’t include it, the soundtrack on CD does.
The slow movement with oboe solo from Bizet’s Symphony in C that accompanied the naturist scene in Pane e Cioccolato (Bread and Chocolate). It was surprisingly direct and effective in its naked simplicity.
Cheating more than a bit here with a TV show, but I always liked the musical recap at the end of season 3 of Reboot done to the tune of “I Am the Very Model of a Modern Major-General” (from G & S’s 1879 opera The Pirates of Penzance).
The best known segment of “The Thieving Magpie” was also used for a sequence in* Once Upon a Time in America* (1984).
Brahms’ Violin Concerto in D Major was used to great effect in There Will Be Blood, especially at the end.
I suppose Beethoven in A Clockwork Orange is also ineligible? Can we give it another honorable mention?
Rollerball had great stuff. Bach should always be played before sporting events. And it also used my personal favorite, Adagio, by Albioni/Giazotto.
That piece gets used a lot. The Trial also featured it. As it’s only musical accompaniment. but it worked.
Approved.
Another musical moment I love, is from Babe: the song the farmer sings to the pig, and which returns triumphantly in the soundtrack at the end. I think it’s from a Saint-Saens organ concerto but heavily modified; perhaps someone who’s familiar with both Saint-Saens and family comedies can elaborate.
Dangerous Liaisons had many such moments, including this scene where Glenn Close realizes, even before he does, that John Malkovich is falling in love with Michelle Pfeiffer: - YouTube
I always liked the use of Schumann’s “The Happy Farmer” in the opening scenes of The Wizard of Oz.. It was the one piece I mastered when I was taking piano lessons.
It is an adaptation of the main theme from the finale of Saint-Saens Symphony #3 (aka “Organ Symphony”). Here is the transition from the scherzo to the finale link the “Babe” theme starts at 28:49 first in a quiet “watery” version featuring four hands at the piano, then fortissimo on the organ and full orchestra. One of the greatest moments in all of classical music. Saint-Saëns said “I gave everything to it I was able to give. What I have here accomplished, I will never achieve again.”
Barber’s Adagio for Strings in Platoon
The overture from The Marriage of Figaro is used to great effect in Zombieland, during a scene where the main characters smash up a souvenir shop to take out their frustrations.
Machete used ave maria to ridiculous effect.
It needs to be said at least one more time. The use of “Ode to Joy”, in various forms, throughout the movie is masterful.