E-Mu Ultraproteus Operation Manual page 106

PRESET PROGRAMMING
MODULATION
Modulation means to dynamically change a parameter, whether it be the
volume (amplitude modulation), the pitch (frequency modulation), or whatever.
Turning the volume control on your home stereo rapidly back and forth would
be an example of amplitude modulation. To modulate something we need a
modulation source and a modulation destination. The source is your hand
turning the knob, and the destination is the volume control. If we had a device
that would automatically turn the volume control, we would also call that
device a modulation source.
UltraProteus is designed so that for each of the variable parameters, such as the
volume, there is an initial setting which can be changed by a modulation
source. Therefore in the case of volume, we have an initial volume and we can
change or modulate that volume with a modulation source. Positive modulation
Adds to the initial amount. Negative modulation Subtracts from the initial
amount.
The main modulation sources on UltraProteus are Envelope Generators, Func-
tion Generators and Low Frequency Oscillators. In the example above, an
envelope generator could be routed to automatically turn the volume control as
programmed by the envelope. Or, a low frequency oscillator could be routed to
automatically turn the volume control up and down in a repeating fashion.
Turning the volume control back and forth on your home stereo is an example of
Amplitude Modulation.
70 UltraProteus Operation Manual