Moog Music Recording Equipment MF-105 User Manual

ENVELOPE GENERATORS

 

     Now that we have explained the MuRF’s filters, let’s proceed 

with some more definitions to explain the Animation function of 

the 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. 

     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 MuRF, there are 8 Envelope generators, one for each 

filter, that shape the Volume of that Filter’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.