ENVELOPE GENERATORS
Now that we have explained the Bass MuRF’s lters, let’s
proceed with some more denitions to explain the Animation
function of the Bass MuRF.
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 - a representation of a Volume Envelope
An “Envelope
Generator” is a circuit
that creates a shape
that corresponds to the
changes in a musical
sound. 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 that control to shape
the start and end of that musical sound. An Envelope Generator is
started by a trigger - a signal used to start the envelope shape.
In the Bass MuRF, there are 8 Envelope generators, one for
each lter, that shape the Volume of that lter’s signal. The
shape of the Envelopes are all determined by the setting of
the ENVELOPE Control. When the Envelopes are started is
determined by the PATTERN selected. To understand that, let’s
continue.
