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Bitwig Envelope-Follower Modulator - Follow Audio Amplitude Shapes

Bitwig Guide | Apr 28, 2022

The Envelope-Follower modulates parameters by tracking the volume shape of incoming audio, using settings like rise, fall, RMS, or peak to fine-tune its response. It only processes direct audio input, not audio from other tracks, unless you use additional tools like an audio receiver. For true sidechaining with external sources, it's best to use an audio sidechain modulator.

You can watch the Video on Youtube

Short Overview

I use the Envelope-Follower to shape effects based on the audio signal right before the device, like adding dynamic control to a reverb from the sound of a polysynth. This lets me modulate parameters according to the volume and contour of the audio, using settings like rise, fall, RMS, and peak for precise control. Since there’s no traditional sidechain input here, I can only work with the direct signal, but if I want to react to audio from another track, I'd use the audio sidechain modulator instead.

Understanding the Envelope-Follower

In this video, I explored the functionality of the Envelope-Follower in an audio production environment and explained how it differs from a traditional audio sidechain input. The Envelope-Follower analyzes the audio signal that comes directly before the device it's placed on, rather than taking input from a separate sidechain source.

Placement and Signal Path

I clarified that the Envelope-Follower will only process audio from directly upstream in the signal chain. For example, if I place the Envelope-Follower after a polysynth with nothing preceding the synth in the chain, the Envelope-Follower has no audio to analyze, which makes it ineffective in that position. However, placing it after an effect like a reverb, which is being fed by the polysynth, allows it to function properly. This is because it can now respond to the audio signal generated by the polysynth and processed by the reverb.

How the Envelope-Follower Works

The core function of the Envelope-Follower is to track the contour or 'envelope' of an incoming audio signal. It offers controls such as rise (attack) and fall (release or decay), which allow me to shape how tightly it follows the incoming audio changes. Additionally, I can adjust the gain to control the overall influence the detected envelope has on modulation targets.

RMS vs. Peak Detection

I also discussed different modes that the Envelope-Follower can operate in, RMS and Peak. In RMS mode, the Envelope-Follower responds to the average amplitude of the audio signal, making it smoother and less reactive to quick, sharp spikes. In contrast, Peak mode makes the Envelope-Follower react instantaneously to any changes in amplitude, allowing for a more precise, but potentially more erratic, tracking of the audio's dynamic changes. The shape of the envelope can be further smoothed using the rise and fall parameters.

Practical Modulation Uses

Once the desired envelope is detected, I can use it as a modulation source for other parameters within my devices. For instance, I demonstrated how the Envelope-Follower's output, shaped by the original audio signal, can control the wet/dry mix of a reverb. In essence, the dynamics of the polysynth’s output determine how much reverb is applied in real time, leading to dynamic, responsive effect processing.

Audio Sidechain vs. Envelope-Follower

A key distinction I made is that the Envelope-Follower in this context does not offer a dedicated audio sidechain input, so it cannot respond directly to signals from other tracks. This limits it compared to an audio sidechain modulator, which is specifically designed to take modulation cues from other sources within a mix.

Creative Workarounds and Limitations

I explained that if I want to mimic sidechaining behavior, I can, in some circumstances, use an audio receiver to bring in external signals to the device chain. This approach involves mixing in external audio material with the signal path, but it has its limitations and may not always suit every production scenario.

Conclusion and Further Learning

In summary, the Envelope-Follower is a powerful device for modulating parameters in response to the dynamics of an audio signal, but it lacks the flexibility of a true sidechain input. For classic sidechaining needs, such as ducking effects or cross-track modulation, I recommended using an audio sidechain modulator and noted that additional videos are available for deeper exploration of sidechain techniques.

This detailed overview should give a comprehensive understanding of how and where to use the Envelope-Follower, its strengths and limitations, and how it fits into a broader sound design context.

Full Video Transcription

This is what im talking about in this video. The text is transcribed by Whisper, so it might not be perfect. If you find any mistakes, please let me know.
You can also click on the timestamps to jump to the right part of the video, which should be helpful.

Click to expand Transcription

[00:00:00] The Envelope-Follower works kind of the same as the audio sidechain, without having an audio
[00:00:07] sidechain or sidechain input here.
[00:00:11] This Envelope-Follower only takes audio from in front of the device.
[00:00:15] So in front here of the polysynth we don't have anything, so it doesn't make sense.
[00:00:21] But we can put this here on the reverb for instance, because we get audio from the polysynth
[00:00:28] itself.
[00:00:29] Right, so we get here a signal, and you can follow the envelope of the sound, shaping
[00:00:38] it with the rise and fall attack and decay setting, increase the gain a bit, and then
[00:00:48] use this shape or the signal to modulate something.
[00:00:58] So the shape of the audio coming from the polysynth decides of how much you mix in this
[00:01:04] reverb here.
[00:01:07] That's also of course the RMS or peak setting here, RMS is basically the average value of
[00:01:12] the audio signal, and peak is basically reacting instantaneously to all kinds of changes in
[00:01:18] the waveform, but you can smooth this a bit out here with the rise and fall setting.
[00:01:23] So the Envelope-Follower follows the envelope of an audio signal, and you can take the signal
[00:01:29] then and modulate something in your devices.
[00:01:32] But you need an audio signal as an input, there's no sidechain here where you can take
[00:01:36] something from some other tracks.
[00:01:41] So for that you probably just want to use the audio sidechain, or you can use here maybe
[00:01:49] the audio receiver and take audio input from a different source, and then you mix in basically
[00:01:56] the source, the audio material from some other channel with your audio signal from your polysynth
[00:02:04] here.
[00:02:05] But that's only usable in certain circumstances, but just to give you an idea how this works.
[00:02:11] So if you want to have sidechain here, then just use the audio sidechain modulator, there's
[00:02:17] also other video on this channel here, we can look up how this works.
[00:02:21] (gentle music)