envelopefaser

The envelope follower, often referred to as an envelope filter or envelope tracker, is an audio processing tool used in sound synthesis and effects to dynamically control parameters based on the amplitude envelope of an input signal. It is particularly useful in synthesizers, sound design, and electronic music production, where real-time modulation of pitch, filter cutoff, resonance, or other parameters is desired.

An envelope follower operates by analyzing the amplitude of an incoming audio signal and generating a control voltage or data stream that reflects its changes over time. This control output can then be routed to modulate other parameters in a sound system. The device typically includes a detection circuit that responds to the amplitude variations, often with adjustable sensitivity and attack/release times to shape how quickly it reacts to changes in the input signal.

In analog synthesizers, envelope followers were originally designed to track the amplitude envelope of a note played on a keyboard or other controller, allowing for expressive modulation of sound parameters. Modern digital audio workstations (DAWs) and software synthesizers often include virtual envelope followers as plugins or built-in modules, enabling similar functionality in a software environment.

Envelope followers are commonly used in sound design to create dynamic textures, such as simulating the behavior of physical objects or enhancing the expressiveness of synthesized sounds. They can also be applied in effects processing to add movement and variation to static or repetitive audio material. For example, an envelope follower can modulate a filter’s cutoff frequency to mimic the natural resonance of a room or instrument, adding depth to a sound.

While envelope followers are distinct from traditional envelope generators (which follow a predefined ADSR curve), they share the concept of dynamic control. The primary difference lies in their responsiveness to the input signal rather than a fixed timing pattern. This makes envelope followers particularly valuable in scenarios where the input’s natural amplitude variations should dictate the modulation of other parameters.