No effect is as organic as reverb. Every sound reflects off surfaces and comes back to the listener. The time it takes to do this creates a feeling of aural space. A great concert hall is made specifically to control the reflections and provide a rich, warm reverberation. Electronic devices, hardware, and software try to emulate this sound. In recording, it's one of the most commonly used effects, and it's almost universally necessary for some instruments, especially voice. When mixing, reverb has the effect of bringing certain sounds to the foreground or pushing them to the background of the mix, in addition to creating a natural ambience.
The Basics of Reverb
Reverb is a very fast echo. However, there are many different types of reverb today. They fall into two categories: room emulations and “old school,” such as plate and spring reverb. Room emulations try to re-create how the sound reverberates in rooms of different sizes. The larger the room, the larger the natural reverb you'll get. You typically see “small room,” “medium room,” and “hall” as popular reverb choices. In the early days of recording, reverb was simulated by sending the audio either through a spring or on a large plate of metal to simulate the sound of reverb. Spring and plate reverb have their own distinctive sounds and are now emulated by modern reverb processors and plug-ins.
Reverb and New Technology
One of the really amazing new technologies in reverb is called convolution. Convolution takes an audio snapshot of a real room (typically recording the sound of a starter's pistol) and mathematically re-creates that room in software. This is called an impulse response. When you get a convolution reverb, you can download different rooms as impulse response files. These rooms range from famous recording studios to historic spaces like Carnegie Hall. You won't believe your ears—it sounds like your music is inside these real rooms. One of the best convolution reverb plug-ins is Altiverb, although many DAWs like Logic Studio are shipping with included convolution reverbs.