The more 'minimalist' films you experience - by the Dardennes Brothers, say, or Lisandro Alonso and Chantal Akerman - or films with little or no musical soundtrack (The Birds, for example), the more music is exposed as the least important of all Cinematic tools.
"Do films need music" might be a disingenuous question. "Would this film be better without music?" is a better, more pertinent one. In Let the Right One In it felt like an unwelcome visitor. In L'Intrus, an imposter. Music in the former reiterated what we were seeing. In the latter it attempted to mask narrative emptiness with faux mysteriousness. In my mind music had slowly become superfluous, retreating to where it is the story, as in some silent films, or, of course, Musicals.
Or should the question be posed from another angle: "Have you seen a film that you thought would benefit from more music?" I don't think I have.
What is music used for? To aid comprehension (as a guide); to add meaning or excitement by amplifying or counteracting the predominant text; to anticipate an attack (in a horror film) unforeseen by the character; to speak the unspoken; to help you remember the film (an aide memoire). Most of all it is there to be entertaining in and of itself, regardless of its relationship to the rest of the film. For me, saying "but it's a great tune" is not enough.
Considering the root reasons for needing music in these cases we can conclude that music improves. However, though it improves, it puts a cap on the potential of the story to be told in the most effective way possible. In other words music is a band-aid on a broken leg.
Music is too often used to validate a flimsy moment, to paper over cracks, to suspend or distract disbelief. Therefore the problem with extra-diegetic (deriving from outside the fictional world of the film) music is partly fundamental, partly in how it is conventionally utilised.
I believe, even when it is making up for something missing or getting our toes tapping, that music generally closes space, suffocates a film by limiting its emotional palette. Clearly music does not come from the fictional world. It is a screen that stands in the way of a more direct engagement. It's good to be in a character's head for a while, where there's no music.It is, undeniably, an especially artificial part of film. Can music be as exploratory, curious and deep as the human mind or heart? Does it expand our horizons or simply take our hand to point at specific sights, 'manipulating' us?
Is it an exaggeration to say that music turns us from witnesses of people and place (even if that is also a controlled, sealed environment) to consumers of those same objects packaged as a product? Yes, music inevitably changes what we see, but what films use music to spice a situation or to undermine, balance, critique, deepen rather than mirror? It seems that a Director, going to a composer, will ask that composer to 'match' what is on screen rhythmically and tonally.
As it is most soundtracks endorse their existence by the following logic: the music is cool, tense etc. and so one thinks the film would be boring without it. The film though is geared towards the inclusion of music and so that is, in fact, true. Why do we say it would be boring without it? What is it hiding?
Is the ubiquitousness of music about control? When there is no music or even no sound, we start to think. We think all kinds of things that take us away from what the film-maker intended or wants us to think or feel. Understandably, artists can be scared of that silence. Their vision needs to be clear and clearly communicated. The music shepherds us back onto the beaten track.
By its nature and by its use music is damaging many films. Of course there are exceptions. Sofia Coppola uses music with ease and style to comment, critique and enrich (and to get us humming along). She demonstrates that the creation of a soundtrack does not have to be an afterthought.
Action and Science Fiction films imbibe music into their fabric most effectively. Nevertheless, imagine Star Wars with its incredible sounds as the music. What would it be like?
Perhaps there are moments, because film will always be a distant world through a looking-glass, that require a soundtrack. Maybe music is needed when we would otherwise have to physically be there to fully comprehend events.
Below is a link to the iconic 'shower scene' from Psycho - once with music in place, once without music:
Psycho Shower Scene
The first, with music, is a tour de force. It is an entertainment. The second is bare and nude and exposed. As Grace Zabriskie says in Inland Empire, it is now a "brutal f***ing murder". The choice is yours.