Studio Techniques - Envelope Follower

An envelope follower it's a circuit that creates an envelope based on the amplitude of an input signal. It's commonly used in vocoders ( to create an envelope based on the speech signal ) but normally this feature is overlooked by user because it's made internally.
It's a very useful tool because allows the machines to interact with the real world. This video by MoogMusicInc shows how to create rhythmic filter patters based on a drum track. The envelope follower detects the amplitude of the signal and transforms it on a control signal that can be connected to a filter control input so the filter cut-off will response rhythmically.

Moog - Dance Music Applications of Rhythmic Filter Modulation

Text from the video :

• The MF-101 Low Pass Filter's ENV OUT Control Voltage makes a number of amazing Rhythmic Modulation techniques possible. This video shows some of these applications in a Dance Music setting. This technique is not limited to Dance Music. The applications are as endless as your imagination.

Source :

• Youtube.com by MoogMusicInc

More info about :

• Wikipedia.org
• Soundonsound.com ( Synth Secrets )
• Angelfire.com ( Envelope Follower schematic )
• Synths'r'us Rene Schmitz DIY ( Envelope Follower schematic )