Apple MainStage 3 Instruments - MainStage 3 Instruments

Filter slope
A filter will cut off the signal at the cutoff frequency you set. This cutoff doesn’t happen abruptly
but rather at a given slope, which is measured in decibels (dB) of gain reduction per octave. You
can define how steep the “cliff” is at the cutoff point by choosing a severe or gentle slope.
Cutoff frequency
24 dB/Oct 12 dB/Oct 6 dB/Oct
Envelopes in the amplifier
Amplifier envelope overview
The amplifier module of a synthesizer is responsible for controlling the level, or loudness, of the
signal over time.
Consider the sound of a violin, for example. The sound slowly ramps up to a peak, or maximum,
level as the bow is dragged across a string, then it is sustained for a period until the bow is
moved away from the string, at which point it cuts off abruptly.
In contrast to the violin example, hitting a snare drum with a drumstick results in a very fast
peak level with no sustain portion, then the sound immediately dies out—although there will be
some decay, the time it takes to fall from the peak level.
These two sounds clearly have different characteristics over time.
Synthesizers emulate these sonic characteristics by providing control over different parts—the
beginning, middle, and end—of a sound’s level over time. This control is achieved using a
component called an envelope generator.
Note: Envelope generators are not limited to controlling signal amplitude. They can also control
the rise and fall of the filter cutoff frequency or they can modulate other parameters. In short,
envelope generators can be used as a modulation source—or as a “remote control” for a given
parameter. See Modulation overview.
Appendix B Synthesizer Basics 486