In the musical piece "The Kiss" by British composer Michael Nyman, these lyrics are heard:
"Images were introduced, because many people cannot retain in their memories what they hear, but they do remember if they see images..."
This is very true as many times I have heard musical pieces and never thought them remarkable, but once I heard them in a film, accompanying images or even just hearing them while looking at a still image, they became instantly associated and indelible. The reverse is most definitely the case in cinema where images may be seen, but the only images that remain in people's mind's are those accompanied by music. However, that music must be memorable itself, otherwise, as in today's cinema, the music and image blend into an amorphous, forgettable soup. Melodies are something which are largely lost in today's film scores, which instead favor soundscapes and "mood" pieces. Either that or they are the most generic "romantic" scores, to the point where they are like emotional white noise. A different shade for each kind of scene, no emotional or psychological depth. There are still Wagnerian sized orchestras but scarcely any Wagnerian leit motifs, small themes associated with characters and ideas. I have heard some attempts in recent films, but they are so meandering as to be dead on arrival. Simplicity is sometimes very much the foundation to build on for a memorable score. Take, for example, Jerry Goldsmith's score for Logan's Run (1976). Before any defined images are seen, there is the sound of the main, three note motif embodying the city and all within. With just these three notes, Goldsmith constructs endless variations, all of which complement the imagery and allow them to become associated. In this suite, listen for how many variations of the main theme there are:
I would say that music is 40, sometimes 50% responsible for the success of a movie. However, there is such a thing as too much reliance on music, especially when the actual images themselves are not all that compelling so the composer has to compensate. An excellent Youtuber has created this series of videos on the importance of John Williams, a composer Steven Spielberg owes the success of his entire career to:
Music, when necessary, doesn't need to be a full orchestra, but it always has to service the film. Sometimes scores can get carried away and become full of themselves. The scores for the westerns of Sergio Leone owe their success to Ennio Morricone, yet many people overlook some of his more subtle scoring, like for John Carpenter's The Thing (1982).
The Thing mostly relies on subtle paranoia and fear, which is what the score draws on and exploits. Though it does use ominous synthesizers and singular guitar notes, there is still a concrete motif which is recognizable throughout the film. In the case of Bernard Herrmann, who added a psychological approach to film scoring, the shower scene in Psycho (1960) would have been disturbing at best without the now obvious, piercing strings. His score for Vertigo (1958) built on Wagner's Tristan und Isolde and created fathoms of desire with the 'Scene d'Amour' cue from the film. Today, an "atmospheric score" is something filled with unremarkable, atonal passages, but for Herrmann, it could be a score filled with themes and melodies and was all the more menacing for it:
Some films that aren't considered the best movies ever made are still saved and elevated by their scores. For example, two scores by John Barry, Moonraker and The Black Hole, both from 1979 and both visually interesting but only half decent films, were rescued by extraordinary music on both counts. Speaking of John Barry, though Monty Normal composed the original James Bond theme, it was Barry who orchestrated it into what it is now famous as. Barry also helped mold the Bond sound and his music was always integral in the Bond films he composed for, in turn shaping the Bond character of those films.
We'll be in a new age of classics again when film scores are given more importance and film composers begin utilizing the same techniques which made the older classics so timeless and memorable. You could take any film that's at least modestly admired and look at it's score and see that it's a contributing factor, anything from Alphaville (1965) to Danger: Diabolik (1968). Lastly, I'll end here with a scene from a film where the separation of either image or music would be unthinkable (and the film where the title of this article came from):