The envelope followerвЂ™s internal electronics actually resemble a VU meter circuit in many ways. You can compare it to a standard VU meter, which indicates the вЂaverageвЂ™ volume of an audio signal in a visual display. Envelope Follower with input and output waveformsДЄn envelope follower provides a control voltage signal in response to the instantaneous вЂloudnessвЂ™ of an audio signal input.

Thus we can breathe new life into systems that were previously quite limited, and produce genuinely new sounds that are qualitatively superior and different from those we now work with.ДЇig 1. As we gain more insight into the nature of musical sound processes, we are able to develop systems which allow more effective use of the basic building blocks of sound processing. Basic inventions in the field of sound modification, as in any other technological area, are infrequent but technological improvements of existing devices and systems are much more accessible. Musicians and recording engineers are constantly searching for sounds that are not just new, but useful in expanding their musical expression and palette of sound colors. In the same way that a simple bandpass filter can be turned into a complex вЂ“ and very versatile parametric equalizer, so the system elements of an Envelope Controlled Filter can be expanded in form and function to provide a very sophisticated musical effects processor. We are accustomed to thinking of them вЂ“ and using them as вЂautomatic wah-wah pedals,вЂ™ but this usage has been dictated by the forms of products available rather than the musical possibilities inherent in the Envelope Controlled Filter as a signal processing system. As the technically oriented musician is well aware, increasing your musical/sound options is both necessary and great fun.Д®nvelope controlled filters have been used by musicians since 1972.

In the article that follows, we will discuss one of the most important of these tools вЂ“ the envelope controlled filter. Over the last decade we have seen innumerable new pieces of sound-altering equipment hit the market, the studio, the stage, вЂ¦the pocketbook.

By Mike Beigel and Elliott Randall (MIX Magazine 1980)

What is an envelope filter