MIDI-Controlled Voice Effects
- Several types of effects processors are designed specifically for the human voice. Dedicated vocal effects are generally digital, and the overdrive and envelope filters used in guitar and bass effects are not so well suited to vocal use. Vocal effects tend to focus on pitch control and complex timbral shaping, which require the additional power of digital processors.
- The Vocoder is one of the earliest dedicated vocal effects, heard on countless records in the 1960s and '70s. The Vocoder is essentially a filter, where the operator adjusts the level of the frequency control by matching the frequency of a separate incoming signal --- usually from a guitar or keyboard. Early versions required an actual audio signal to manipulate the filter controls, but modern digital versions allow for programming via MIDI. This capability allows a variety of new control systems; for example, vocalists can control the effects applied to their own voices using a MIDI controller with rotary dials or a small track-pad.
- Pitch shifters were initially used on instrument effects, such as the popular Digitech "Whammy" unit, using a traditional rocker pedal. Modern PC-based equivalents allow pitch control from MIDI devices.The ability to snap the pitch of a voice to a specific chromatic pitch is a useful tool for singers --- particularly in a live setting. It allows vocalists to match the pitch played by the instruments, even when outside their natural range.
- Harmonizers make several copies of an incoming vocal signal. It then raises and lowers the pitch of the signals by different amounts and recombines them to create a "chord" meant to resemble the sound of a choir. The relative pitches of all the different voices can be controlled via a keyboard, playing traditional piano chords, or by selecting the desired key from an on-board rotary control. Some modern harmonizers automatically detect the relevant harmony key by listening to the incoming audio.