User`s guide

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The Envelope Follower has two parameters: a time constant (in
milliseconds) and a threshold (in percent).
The time constant specifies how rapidly the output tracks variations
in the source signal’s amplitude. A fast time constant (such as 5 ms)
will respond quickly to changes in amplitude, but the result may be
somewhat rough. A slow time constant (such as 200 ms) will be
smoother but may be somewhat sluggish to respond.
The threshold percentage acts like a noise gate. When the calculated
envelope of the input signal falls below the specified amplitude (say,
10%), the output signal will be greatly attenuated. Amplitudes above
the threshold are unchanged. Most Envelope Follower patches set
the threshold percentage to 0%, making it inactive.
The following illustration shows the effect of setting the threshold
to 24%, given an Envelope Follower output that would otherwise
look like a sawtooth wave:
The output of the Envelope Follower is converted to a bipolar signal.
Silence, when envelope followed, will produce a –100% level. A loud
waveform will produce a positive signal level.
The beauty of the Envelope Follower is that it allows a sound to
generate its own control signal. The Envelope Follower is useful for
producing a number of effects in which the modulation depth
changes in response to the signal’s amplitude. This can result in
less-mechanical-sounding tremolos, vibratos, and many other
effects.
You can make almost any effect subtler or more interesting with
judicious use of the Envelope Follower. Examine some effects in the
Envelope Follower category for examples.