Apple Soundtrack Pro - Manual (Page 202)

202 Chapter 9 Working With Audio Effects
Phase Shifters
Phase shifters produce a characteristic “whooshing” sound by combining the original
signal with a copy of the signal that is slightly out of phase with the original. This
means that the amplitudes of the two signals’ sound waves reach their highest and
lowest points at slightly different times. The time between the two signals is
modulated, typically using an LFO. As the two signals go in and out of phase, certain
frequencies, called notch frequencies, are created, which give phase shifters their
distinctive sound.
The main difference between chorus and phase shifting is the amount of delay time.
Chorus effects typically use delay times between 20 and 30 milliseconds (ms), while
phase shifters (and flangers, discussed next) typically use shorter delay times, between
1 and 10 ms.
Flangers
Flangers work in much the same way as do phase shifters, but additionally change the
pitch of the delayed signal slightly. Flanging is typically used to create a more extreme
change than phase shifting, sometimes described as adding a “spacey” or “underwater”
effect.
All of the modulation effects include parameters for the delay rate (also called speed or
frequency), which let you set the minimum delay time; depth (also called width or
intensity), which you use to set how much the LFO modulates the delay time; and mix,
which you use to control the ratio of the effected (wet) signal to the original (dry)
signal. They can also include parameters for feedback (or regeneration), which add part
of the output back into the input signal.
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).