Broadening Horizons
The first 20 minutes of The Wizard of Oz is in black and white, not because of technological limitations or the '30s audience's sensibilities, but for dramatic effect. It's used to express how otherworldly and vivid the land of Oz is to Dorothy.
It's a visual effect (dubbed by TVtropes as Deliberately Monochrome) that we don't see too often, I personally have only seen it recently in a couple anime classics, The Melancholy of Haruhi Suzumiya, and Clannad. Interestingly, both of these examples use the technique to show the brilliance of a single character, not a place or mental state.
But what I want to talk about is that you can create this same kind of world-widening contrast in music, just as you can in film, though a specific use of dynamic contrast. And I would bet most people would agree that the aural effect of making something Deliberately Monochrome is way more pronounced than the visual form.
Dynamic contrast is an important element of music. Everybody (well, mostly everybody) hates over-compressed music, or songs that have the same volume and feel throughout. Dynamics can create or augment dramatic structures, allowing finales to be climatic and calm resolutions to be...resolute.
But there's one use of dynamic contrast that causes something peculiar psychologically. When you queue up a song and hit play, you subconsciously begin to make assumptions about the sonic world that song inhabits. It only takes a few seconds, and then your mind just says to itself, "ok this is what this song is like." Songs can break that assumption by starting off quiet and thin, then suddenly and sometimes violently going loud and full. These songs always tempt you to turn up the volume. If the musicians and engineers go ham on this moment, you haven't just gone from monochrome to color, you've relearned of 3D space, a much wider spectrum of color, and broken the limit of how loud you thought the song would be, all in an instant.
Welcome to Oz.
Unlike the rare uses in film, this effect in music is fairly common. Taking a quick look through my library, some great examples of this technique are the intros of:
Pink Floyd's The Wall
Peter Gabriel's Up
Blink's eponymous album
Queens of the Stone Age's Songs for the Deaf
The effect that this can have is shocking, oftentimes literally jumpscaring people. It's far more visceral than it's visual cousin.
