Moog Music MF-105M MIDI MuRF (Manual Addendum - Firmware v1.8) - Manual (Page 10)

ENVELOPE GENERATORS
Now that we have explained the MIDI MuRF’s filters, let’s proceed
with some more definitions to explain the Animation function.
The term "Envelope" is used to describe the changes that occur to
a musical sound, from its start to its end. A musical sound can have a
rapid onset, like the plucking of a string or the striking of a drum. It can
also have a gradual onset, like a slowly bowed violin. With the term
"Envelope", the shape of the start of a sound is called the "Attack". The
end of a sound can have different shapes as well – it can be abrupt, like
on an organ, or it can be very gradual, fading out like a piano note held
down. The shape of the end of a musical sound is called "Decay". Both
Attack and Decay are time-related, and can be measured in seconds or
milliseconds. Figure 9 illustrates the components of an envelope.
Figure 9 - Envelope
An "Envelope Generator" is
a circuit that produces a control
voltage that corresponds to the shape
of a musical sound’s envelope. The
signal that comes out of an Envelope
Generator is sent to a control, such as
volume, and is used to automatically
turn up and down the volume to shape the start and end of a musical
sound. An Envelope Generator is started by a trigger - a signal used to
start the envelope shape.
In the MIDI MuRF, there are 8 Envelope generators, one for each
filter, that shape the Volume of that Filter’s signal. The shapes of
the Envelopes are all determined by the setting of the ENVELOPE
Control. The timing and sequence of the Envelopes is determined by the
PATTERN selected. To understand that, let’s continue.
SEQUENCERS and PATTERN GENERATION
A Sequencer is used to generate reoccurring rhythmic patterns, often
by triggering sequences of notes in synthesizers or drum machines.
However sequencers can be used for purposes other than triggering
notes - they can be set up to create reoccurring changes of timbre as
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