Well, Lack Thereof
Despite the name, silent films were often anything but silent. In the really early years, theaters would employ piano players to provide accompaniment for the film. As the medium grew, larger theaters would host full orchestras, and studios might hire composers to write scores to be played live during the show (source).
All Quiet on the Western Front was released when synchronized dialogue was being introduced to audiences—just four years after Don Juan (1926), the first feature-length film to used a synchronized soundtrack throughout its runtime, and three years after The Jazz Singer (1927), the "first feature-length Hollywood 'talkie' film in which spoken dialogue was used as part of the dramatic action" (source).
Given the long love affair between movies and music, it must have been very surprising to 1930s audiences that director Lewis Milestone would choose to include very few musical compositions in All Quiet. We know it surprised us.
The Sound of Silence
For most of All Quiet's more than two-hour runtime, there's no background music. No shrill strings to punctuation moments of horror, no melancholic strings to accompany moments of loss, no full orchestra crescendos to announce moments of heroic triumph. No nothing.
You'd think this would make All Quiet all, well, quiet, but Milestone does add sound his film. He just does so diegetically (source).
Let's clarify our jargon: the word "diegetic" means some sound that originates from within the film's world—in this case, sounds like gunfire, screaming, and the squishing of mud. This is opposed to "non-diegetic" sounds, which include mood music.
In the absence of non-diegetic music, All Quiet is orchestrated by the sounds of war: the percussion of marching soldiers, the stretches of silence before an offensive, and, of course, the trill of incoming shells.
Milestone lets the "music" of war speak for itself. Rather than use mood music to clue the audience into how they should feel, he respects them enough to let them draw their own conclusions.
With a film that's been cut and re-edited as much as All Quiet on the Western Front has, viewers throughout the decades have seen different versions, with different scores. During its initial release, some theater owners added their own music to the film, and when the film was played on TV in the '50s, music was included in the final scenes against Milestone's wishes (source).
But the version of All Quiet you've most likely watched is the talkie version restored by the Library of Congress's Motion Picture Conservation Center. This version contains two musical cues, one at the film's opening and the other at its ending.
The film's opening music accompanies the soldiers as they parade through the city streets. The music's upbeat, with the militaristic flair of marching drums and proud trumpets. It represents the nationalistic pride felt by the soldiers and cheering citizens.
It also cues us in to the optimistic mindset of the populace as it views the war as something to celebrate. The music is pure patriotism, and as the camera slides into Kantorek's classroom, the music fades and is replaced with Kantorek's lesson, which is equally chauvinistic in theme.
The film's ending music is a stark contrast to the opening. Rather than a proud martial march, the final scene is accompanied by a single, mournful harmonica. The harmonica represents Paul's state of mind in this final scene, depressed over what the war has done to his life and the lives of his friends.
Yup: nothing more depressing than a harmonica. (Sorry, Bob Dylan. It's true.)
Man With the Credit
David Broekman's credited with All Quiet's synchronization and score. Broekman's movie credits begin in the transitional years between silent and talkie films, with the majority of his work concentrated in the 1930s.
He worked as a composer for films such as White Hell of Pitz Palu (1929), Tarzan the Tiger (1929), and Outside the Law (1930). Throughout the '30s, he also worked on synchronization and as a musical supervisor.
As we said earlier, silent films were anything but silent, and a silent cut of All Quiet was created for theaters that had yet to upgrade for talkies. In case you have a version of this rare find, know the score for the silent version was composed by Broekman as well.