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Chapter 7: LFOs, S&H and Process
ANDROMEDA A6 REFERENCE MANUAL 179
PROCESS MODULE
The PROCESS module contains the Tracking Generator and
the Engine Optimizer.
TRACKING GENERATOR (TGEN)
The Tracking Generator is used to scale a modulation
source. It allows you to "redraw" any modulation source to
your own custom curves. For example, normally you
could modulate the level of a sound using velocity; the
harder you play, the louder the sound gets. If the amount
of change in volume is equal to the change in velocity, this
would be called linear control (and you wouldn't need the
Tracking Generator). However, if you set the Tracking Generator's input to
VOX KEY
ON VELOCITY
, and then routed the output of the Tracking generator to Envelope 3's
LEVEL, you can make your own customized "map" of the control velocity has over
the sound level. You could even make it turn back on itself—for example, make it
loud at both very high and very low velocities, and softest at average velocities.
When you look at the
TGEN display, you're looking at a classic "X-Y" axis. The input
is on the X axis, from left to right, low values to high values. The output of
TGEN will
be according to the Y axis, from up to down. The Tracking Generator divides the
range of the input into a maximum of 16 points or stages, each of which can be set to a
value between +120 and –120. If you boost the value of one of the lower points, you
can make the input more sensitive in its lower register. By creating a non-linear
curve, or using one of the preset curves available in the Tracking Generator, you can
scale the velocity's control over the sound's volume just the way you want.
Track Gen Level and Track Gen Step
TRACK GEN LEVEL appears as one of the modulation sources in every MOD menu.
As the input to the tracking generator rises and falls, it scales its output linearly
between stages according to the level you set for each stage. For example, if the Pitch
Bend wheel is the TrackGen source, and stage 15 is set to +90 and stage 16 is set to
+120, at the top 1/16
th
of the Pitch Bend range the output of the Tracking Generator
will rise smoothly, from 90 to 120.
When
TRACK GEN STEP is chosen as a mod source, the Tracking Generator's output
is stepped. This means that instead of scaling the input linearly from stage to stage,
the input is kept at each stage's value setting until it goes beyond the following
stage's value setting, at which point it jumps to that setting. In the example above, as
you raise the Pitch Bend wheel to the top, it would jump suddenly from 90 to 120
with no interpolations in-between as it would with
TRACK GEN LEVEL. This feature
is useful in creating "mini-sequences" if the modulation destination is an oscillator
frequency and the Tracking Generator's input is an LFO using an "up sawtooth" as its
waveform.
Tip: The Tracking Generator can be used to turn a variable control, such as the Mod
Wheel or velocity, into a switch by setting all of the points to 0 except the
highest one. Only near the maximum input will anything other than 0 come out
of the Tracking Generator. Note that this doesn't keep you from using the Mod
Wheel directly at the same time for more gradual functions. For example, the
Mod Wheel could be used to gradually bring in vibrato from an LFO, and at the
very top of its travel the Analog Distortion could suddenly be switched on.