Many producers use reverb during the recording process to make vocalists feel more comfortable. Although the vocalists hear the reverb while singing, it can be removed from the final track during the mixing and production stage. Using reverb for nervous vocalists allows them to perceive their sound as fuller and rounder. This makes them think that they sound better and often results in them being less restrictive in their singing.
In general, music with busy or noisy components at fast tempos do not need reverb because it will pollute the sound. For example, a raucous rap song would not need very much reverb, because the vocals in rap music are typically sharp and crisp. Softer music, such as ballads, may need more vocal reverb. If the vocal track of a song has particularly tinny or bright sounds, then reverb can help smooth out the sound.
There are six basic types of reverb: room, hall, plate, spring, chamber and convolution. Plate reverb is the primary type of reverb that is applied to vocals. Plate reverb sends a recorded sound to a metal plate, which vibrates once it receives the sound. The vibrations are turned into an audio signal, which augments the track's sound. Plate reverb is the most bright and clear of the reverbs, which makes it suitable for vocals.
Many times, people use reverb when they should have used another effect, such as delay. As a result of the way the electronic components process sound, delay devices do not produce good reverb for vocals, although it is sometimes used as a substitute. Delay can add an interesting echo effect to music, where repeated lines or words can be heard in repetitive succession. Reverb adds a slight delay quality, but the sounds blend in with the vocalist's voice more so than a delay device.