If you’ve ever wondered what the secrets are behind professional sound, well, unison and octave layers certainly are. Bear in mind that more is not always better. It usually isn’t. But in this particular case, “more” helps confusing the brain better. But why do we want to confuse the brain of the listener? Because it enhances their pleasant perception of the music.
It’s all about the illusion
Think of it as an illusion. Illusion is a big part of all kinds of different arts. Just look at how painters create the illusion of real life lighting by using different colors. People involved in the creative process of music production are true illusionists. Or at least they had the chance to be one, before they came out with that lifeless sounding crap. Anyway. Adding unison and octave voices will create something that’s more than just the sum of the parts. It will create the illusion of a smoother, more in-tune performance. We need this in the middle of the frequency spectrum the most.
While people say it thickens the sound, it’s more like an anti-aliasing effect, so to say. Think orchestras or big bands, or choirs. They have a lot of musicians who play or sing the same thing. Yet in the real world, playing or singing the same thing will still sound somewhat different. The pitches, the attack and decay times, the timbres will all be a little bit different from each other. There’s a good thing about this. Even if the brain would perceive any of these attributes disturbing and out of place on a single voice, when there are multiple voices, it loses touch. Instead of all the little imperfections, it’ll complete the perceived audio image into a summed whole. A whole that is perfect. Pianos have multiple strings in the mid- and high range, organs do the same with pipes, and we have chorus and phase effects, among others. The benefits of these is not just to make sounds louder or stand out more, but to smear the sound into this perfect illusion.
Smear it to perfection
Playing live, in a band with limited amount of members, you have not much choice. You need to come up with the best possible arrangement, or hire as many members as you can. Time will come when you’ll need to stop chasing around those round bottomed backing vocalists though, n00b. Because once it comes to recording and mixing, you have all the control over the listeners’ brain. Live with it.