Sequential Prophet VS - Page 129

129
Filter
As mentioned above, the lter envelope is not responsible for this sound's
changes in timbre. Selecting any control in the Filter group, we nd that the
initial envelope amount is zero. Looking at the modulation grid in the program
form, you will nd that velocity modulates the lter envelope amount. The
lter envelope produces a spike which, with increased velocity opens up the
lter long enough to emphasize the initial noise burst produced by the mixer
envelope.
The lter cuto is set just high enough to make the white noise audible
with low key velocity. Selecting Cuto and adjusting to various values
demonstrates how the programmed value of 62 is suitable for this application.
The keyboard modulation source is set for a medium-positive eect on the
lter cuto. This only aects the tone of oscillator A since the remaining
oscillators all produce sine waves (hence, no harmonics) at frequencies well
below the lter cuto.
LFO Group
As the program form shows, each LFO modulation source modulates a pair
of oscillators. Both LFOs produce triangle waveforms suitable for vibrato, but
are at slightly dierent rates. As notes are held, only oscillators C and D are
heard, so the modulation of oscillator B is not heard. (Oscillator A is noise,
so modulation would have no eect in any case.) Both the pressure and mod
wheel modulation sources control the depth of LFO modulation.
Voice Control
All voices are panned center, and no modulation occurs to cause motion in the
stereo eld.
Program Volume is set at 50 and the velocity modulation source amount is set
to 84, allowing key velocity to drive the volume to its maximum. The amplier
envelope is a simple organ-style "on-o" envelope, with a long alternate
release.
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