Apple Soundtrack - Manual (Page 132)

132 Chapter 8 Working with Audio Effects
Reverb and Delay Effects
Reverbs and delays work by copying a part of the audio signal, delaying it for a brief
period of time, and then playing it back with the original signal. The delayed signal can
be played back multiple times, and can be modified in a variety of ways.
Delay
A delay effect stores the audio signal, and then plays back each repetition at a regular
rate of time after the original signal. Delays can be used for doubling individual sounds
(for example, making it sound as if a group of instruments is playing the same melody),
to achieve echo effects (making it sound as though the sound was occurring in an
immense space), and to enhance the stereo position of tracks in a mix. Delay effects are
not commonly used on an overall mix except to achieve special effects (such as to
create an “otherworldly” sound).
Delay effects let you set the delay time, the time between the original signal and the
delayed signal. Delays often provide parameters for feedback (also called regeneration),
which let you set how much of the delayed signal is fed back into the delay’s input,
creating more repetitions of the delay (like the number of “bounces” in an echo). Specific
types of delay have other parameters: Tap tempo delays let you set the delay time by
physically tapping a key or controller; stereo delays include parameters for the pan
position of the output signal, which can be shifted over time using a low-frequency
oscillator (called an LFO).
Reverb
Reverberation, usually shortened to reverb, simulates the sound of acoustic
environments such as rooms, concert halls, caverns, or the sound of infinite space. In
any acoustic space, sounds echo off the surfaces of the space (the floor, walls, and
ceiling) over and over, gradually dying out until they become inaudible. Reverb effects
consist of thousands of delays, of varying lengths and intensities, that simulate these
natural echoes. Reverb helps define the sense of space in which sounds take place, and
can be used to simulate both realistic and fantastic acoustic environments.
The first form of reverb actually used a room with hard surfaces (called an echo
chamber) to add echoes to the signal. Mechanical devices, including plates and springs,
were also used to add reverberation to the output of instruments and microphones.
Digital sound recording has made it possible to use digital reverbs, which use complex
algorithms (sets of equations) to simulate various acoustic environments with greater
accuracy and flexibility.