Delay/Reverb

Delay and reverb are time-based plug-ins that are typically used as special effects to sweeten a mix that has already been balanced with basic level-setting, EQ, and compression. A delay works by repeating the audio that is played through it, essentially creating an artificial echo. Depending on how the plug-in’s parameters have been adjusted, the echo can be fast or slow, and it can occur once or multiple times. A reverb works by the same principle, though it will typically have a larger set of parameters and place the repetitions much closer together (like a very fast delay), mimicking the natural reverberation that occurs in a real space when sound bounces off of the surfaces around us.

At a bare minimum, a delay plug-in will usually have the following parameters: “time” and “feedback.”

Time, measured in either milliseconds (ms) or note (1/4, 1/8 dotted, 1/16 triplet, etc.), determines the amount of time that will pass between the repetitions. A “time” of 200 ms, for instance, will cause the first repetition to occur 200 milliseconds after the initial sound, the second repetition to occur 400 ms after the initial sound (200 ms after the first repetition), the third repetition to occur 600 ms after the initial sound (200 ms after the second repetition), and so on. When measured in note, the repetitions will occur at intervals consistent with the BPM of the session.

Feedback, usually measured as a percentage from 0 to 100, determines how quickly or slowly the repetitions will fade away over time. A “feedback” value of 100%, for instance, might create an infinite number of repetitions, while a very low “feedback” value might only create one audible repetition.

Most delay plug-ins will have “dry” and “wet” parameters that control how much of the original signal we hear and how much of the echo we hear. Many delay plug-ins will also have additional parameters that control the tone of the repetitions, much like a built-in EQ.

Reverb plug-ins come in all shapes and sizes. In addition to the “dry,” “wet,” and tone-based parameters you might find on a delay plug-in, you might find an array of other various parameters on any given reverb plug-in. The most common are “pre-delay,” “size,” and “density.”

Pre-delay, usually measured in milliseconds (ms), determines the amount of time that will pass before the first repetition. Remember, a reverb’s purpose is to mimic real-life reverberation, so the repetitions that follow the pre-delay will usually be much closer together (often to the point that they run together), but the pre-delay itself is meant to give an indication as to how far the “surfaces” are from which the initial sound is reflecting in the simulated space.

Size similarly determines how big or small the simulated space is. Much like the “feedback” parameter on a delay plug-in, “size” determines how long the repetitions of the initial sound will last. A smaller “size” will create fewer repetitions before they fade, while a larger “size” will create more.

Density, usually measured as a percentage from 0 to 100, determines how close together or spread out the repetitions are over time. A “density” of 100%, for instance, will place the repetitions so close together that, to the listener, they run together. The lower the “density,” the more a reverb will begin to sound like a delay, meaning that the repetitions will be more distinct from one another.

Many reverb plug-ins will have alternative parameters like “attack” and “release,” represented by adjustable lines on a graph, that allow the user to shape the reverberation in a more visual way.

Another common reverb parameter is “spread,” which allows the user to further simulate a real space by adding more or less of a stereo element.

Because delays and reverbs mimic the echoes and reverberation we might hear in a real space, they are often used in a mix to create depth, or the illusion of distance. A long reverb, for instance, will trick our ears into perceiving more space between ourselves and the source of the sound. This can be useful for creating contrast in our mixes between things we want to be perceived as “up front” and things we want to place in the “background,” especially when simple volume adjustments don’t have enough of an impact.