From Austrian-German-American filmmaker Fritz Lang, this classic German thriller, M (1931), often makes it into lists of top 100 best films. I watched it (109-minute version, English subs) after reading how groundbreaking the film was, not just in its production but also in its storytelling. The use of voice-over narration was new at the time, and this was Lang's first sound film. The soundtrack is experimental, and a few scenes are silent—parts where he must've thought the images would more effectively tell the story without sound. He used leitmotif, defined as: A melodic passage or phrase, especially in Wagnerian opera, associated with a specific character, situation, or element. This was new to cinema too, and the most significant use of this device in M is the killer's haunting and recurrent whistling of "In the Hall of the Mountain King," composed by Edvard Grieg in 1875. As if watching a stage play, we hear the melody even while the villain is off-screen, which adds a layer to the foreboding atmosphere.
Watching a film about a serial killer who abducts and murders kids doesn't feel like it should be entertainment. While films in the 1930s weren't as graphic as what we can see today, they exude a certain unsettling darkness that modern movies are unable to reproduce. It's something in their primitiveness, the inventive and oblique ways they suggest rather than overtly show, and possibly also because we're aware most or all of the actors are dead.
When I watched M, I kept in mind one reason Lang made it, that is, to warn mothers about neglect of children (final line: One has to keep closer watch over the children). I'm glad I didn't pass on it; there were a few shots I'd never seen in films of that era, such as when the camera, like a voyeuristic ghost, floats through a closed window, or later when it rises up out of a hole in the floor. I was surprised that in the 30s a shot could continue, uninterrupted by cuts, through such a long room. This was the fly-like camera meandering through the hall of the organization of beggars (not unlike the scene in Martin Scorsese's Goodfellas (1990) when we're introduced to the guys at the Bamboo Lounge). In M, we the viewers enter into that intimate, enclosed and claustrophobic space—into the seedy guts of the metropolis (scene starts at about 41:30 here on YouTube).
Writing a hundred pages on M wouldn't be hard. No doubt film scholars have written volumes on it. A couple parts seemed unnecessarily long to me, but I'd watch it again since it's the type of film that would reveal new edges and facets with each viewing.