E-Mu MORPHEUS, Operation Manual

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Chapter 7: Preset Programming 89
PRESET PROGRAMMING
Consider, as an example, the human vocal tract, which is a type of
complex filter or resonator. There are dozens of different muscles
controlling the shape of the vocal tract. When speaking, however, we
don't think of the muscles, we just remember how it feels to form the
vowels. A vowel is really a configuration of many muscles, but we
consider it a single object. In changing from one vowel to another, we
don't need to consider the frequencies of the resonant peaks! You
remember the shape of your mouth for each sound and
interpolate
between them.
THE Z-PLANE FILTER
In a simple Morpheus filter, we would start with two complex filters
and interpolate between them using a single parameter. Refer to the
diagram below.
The Morpheus Z-plane filter has the unique abilty to change its function over time.
Filters A and B represent two different complex filters. By changing a
single parameter, the
Morph , many complex filter parameters can
now be changed simultaneously. Following along the Morph axis you
can see that the filter response smoothly interpolates between the two
filters. This is the essence of the Z-plane filter. Through the use of
interpolation, many complex parameters are condensed down into
one manageable entity.
This Z-Plane filter sweep can be controlled by an envelope or function
generator, an LFO, modulation wheels or pedals, keyboard velocity,
key pressure, etc. In fact, any of the modulation sources can control
the Z-Plane filter.
Frequency
Amplitude
Morph
A Filter
B Filter
Morph