Reverb adds two properties to sounds – diffusion and depth. While there are many ways of changing the balance between diffusion and depth, there are times when a more extreme approach is required. Reverb may not be the best solution if a sound needs a lot of diffusion but very little depth, or a lot of depth but very little diffusion.
More diffusion, less depth
Diffusion is a way of blurring a sound, reducing its sharpness or distinction. A sound may need to be diffused if it needs to be pushed to the background or to fit it into a mix that is generally quite diffuse. This might need to be done in a way that doesn’t add depth if the background of the mix requires a lot of clarity or if the mix is meant to be very shallow.
In these situations, processes such as chorus, microshifting, slap delay or even true doubletracking can be appropriate.
- Chorus diffuses the sound by adding a copy with constantly-changing pitch and timing. This can be appropriate if the sound will benefit from the added movement and the constantly-changing pitch is not distracting.
- For situations when the movement or pitch modulation are not appropriate, microshifting might be a better solution. This is commonly implemented as a pitch shift of a few cents down on one side of the stereo space and a pitch shift of a few cents up on the other side of the stereo space. This can give a very big sound that stretches across the stereo space, but doesn’t have the modulated sound that chorus adds, and doesn’t have the added depth or tail that reverb adds.
- Slap delay is shorthand for any quick delay with a delay time roughly between 30ms and 150ms. The delay time should be determined by the nature of the sound – the delay time and level should be set so that the delayed sound blends smoothly with the original sound. Slap delay can be useful when a sound needs less diffusion and more depth than chorus or microshifting, but not as much depth as a reverb might add.
- True doubletracking is a process of using two different takes of the same part being played simultaneously. The natural, human variations between the two takes will make them slightly different – different enough to create a different sound when both takes are combined. This is a popular technique for guitars and vocals because it can be used to create a very big sound while still sounding much more natural than applying chorus or microshifting.
Depth, no diffusion
Depth is a sense of distance – particularly a distance between the foreground and background of the mix. A shallow mix will have very little distance between the foreground and background, a deep mix will have a lot of distance between the foreground and background. Usually sounds are pushed to the background by adding both depth and diffusion, but in some cases it is useful to add depth without diffusion. A mix might need to be very deep, but also very sharp and clear (which would require diffusion to be minimised). In other cases,a mix might already be quite diffuse, and depth has to be created by using more obvious means (because regular reverb would be lost in the general diffusion of the mix).
In these situations, delay is often the most appropriate tool. Longer delays (>150ms) should work best. When tuning a delay for depth, rather than rhythmic complexity, it’s often worthwhile tuning it by ear instead of snapping to the song’s tempo. The sense of depth will come from hearing the echos between the notes. This may be difficult if a tempo delay is causing the echos to be perfectly timed to sound underneath foreground elements (so that the background echos are masked by the foreground elements). Making the delay more audible by tuning it in between tempo times will also allow the delay to be at a lower volume. This will enhance the sense of depth in the mix.