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Prophet Rev2 User’s Guide
Filter
The description of envelope behavior just given is true when the amount parameter is set to a positive value. But since this control is actually bipolar, it is possible to
set a negative amount of modulation. In this case, the envelopes are inverted and their
behavior changes. The best way to get a feel for the difference is to experiment with
both positive and negative settings of the env amount parameter.
The cutoff frequency setting may limit the effect of the envelope on the lter. For
example, in low-pass lter mode , if cutoff is at its highest setting, a positive envelope
amount will have no effect on the lter since the lter is already completely open.
Velocity: 0...127—Allows key velocity to inuence lter frequency. If
the amount is set to a positive value, the harder you play, the more the
lter will open and the brighter the sound will be. Conversely, if set to a
negative value, the harder you play, the more the lter will close and the
less bright the sound will be. This control makes for more touch-sensitive
sounds.
Key Amount: 0...127—Sets the amount of modulation from the
keyboard to the lter’s cutoff frequency. Any setting above zero means
that the higher the note played on the keyboard, the more the lter opens.
This is useful for adding brightness to a sound as higher notes are played,
which is typically how acoustic instruments behave. When set to zero,
keyboard lter tracking is off, meaning that lter frequency is unaffected by
playing higher or lower notes on the keyboard. When set to 64, the lter
will track in half-step increments (which can be useful if you are using
the lter to generate a pitch through self-oscillation in 4-pole mode).
Audio Mod: 0...127—Controls the amount of audio from Oscillator 1
used to modulate the lter cutoff frequency. It is useful for adding a bit
of harmonic movement and high end sizzle to many sounds, especially in
4-pole lter mode with some lter resonance.
To create bell-like FM sounds with audio mod, set the lter to 4-pole mode, set
audio mod to 127, set osc mix to 127, set osc 2 shape to off, and set osc 1 shape to the
desired waveshape. Then turn resonance to 127 and experiment different osc 1 freq
tunings, lter cutoff, and key amount settings. Adjust the lter and amplier envelopes
as necessary.