The three essential categories of mixing discussed so far (compressor, equalizer, saturation) influence, in simple terms, the characteristics of waveforms, change the volume of certain parts of the sound spectrum from lows to highs, and their intuitively perceivable characteristics, which are described with linguistic metaphors such as “thin” or “full”, “smooth” or “rough”.

What has been ignored so far is the fact that sound waves propagate in a space. Either they reach a human ear directly, starting from their source, or they are first reflected at other places and are therefore directed to the listener’s point of view with a time delay and only partially. We quickly understand each other when we speak of reverberation in this context. A special case of this kind is the echo, where still recognizable single sounds repeat in a certain number and speed – depending on the distance from reflecting surfaces.

In audio mixing, the more general term delay is used, and its types include reverb and echo.

Here are three tutorials from the Recording Blog, delamartv and Martin Wolfinger on mixing reverb:

Martin Wolfinger also separately discusses the function of reverb for adding depth to a mix:

Big Z gives another English-language overview of essential aspects of reverb/reverb:

If you look at the setting options of reverb and delay, you will find a very wide range of style templates. Their effect is once again very variable in itself, in that the intensity of the application of the effect (optionally plus several parameters) produces quite different results (often up to irritating-disturbing distortions).

Of course, the stereo spectrum also plays a role for spatial effects, through which spatial positions of the sound source are signaled to the ear. Targeted imbalances in the delay to the left and right can also be used, for example, for psychoacoustic volume illusions.

In practice, the term delay often refers to either a limited use as a doubling of sound events at intervals of milliseconds (which already means another means of amplification besides level, compressor and EQ). At the other extreme are relatively long lingering, usually quieter repeats that either subtly create texture in the background to make the overall image fuller (without necessarily being clearly heard out) or are deliberately used to create clearly audible series of sound events. Thus, rather plainly played sequences of sounds can have more complex results. Far beyond the creation of certain realistic spatial illusions (denoted by styles such as “room” or “hall”), delays can then create extremely artificial soundscapes that were unprecedented before the corresponding effects units and plug-ins.