Bitwig Audio-Sidechain Modulator - Dynamic Modulation based on Audio

Bitwig Guide | Apr 29, 2022

An Audio-Sidechain takes an audio signal, such as a kick drum, and transforms it into a modulation signal that can control various parameters on another track, like the volume or filter cutoff of a bass sound. This technique is commonly used to duck the bass when the kick hits, but it can also modulate many other aspects of a sound for creative effects. Using Audio-Sidechain modulation allows for dynamic and interesting sound design, making your music more lively and expressive.

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Short Overview #

When I use the Audio-Sidechain, I can turn any audio signal into a flexible modulation source, not just for ducking the bass with a kick drum. By shaping the incoming signal and focusing on certain frequencies, I can control a wide range of parameters such as filter cutoffs or volume, bringing more movement and interest to my sounds. The setup lets me use any part of my mix, like a kick or even the bass itself, to drive changes in other elements. This approach goes far beyond the classic pumping effect, unlocking creative ways to make my music feel more dynamic and alive.

• The Audio-Sidechain converts an audio signal into a modulation signal.
• Example uses a bass sound from a polysynth and a kick drum.
• The sidechain modulator takes the kick drum's output to create the modulation signal.
• Attack and decay times are controlled using the "Ryzen 4" parameter.
• A band pass filter focuses the modulation on specific frequency ranges.
• The sidechain effect typically reduces the polysynth's volume whenever the kick drum plays.
• Modulation is not limited to volume; it can also target parameters like filter cutoff.
• The Audio-Sidechain can use different input sources, such as the bass itself, for unique effects.
• It enables creative sound shaping by reacting to audio waveforms, adding movement and interest.
• The technique is versatile and encourages experimenting with different modulation targets for more dynamic sounds.

Introduction to Audio-Sidechain Modulation #

In this video, I walk through the process of using an Audio-Sidechain as a modulator within a synthesizer environment. I explain how a simple setup with a bass sound generated by a polysynth and a basic kick drum track can be transformed using sidechain techniques. The Audio-Sidechain is not simply a tool for ducking or reducing the volume of one sound when another plays; it allows much broader creative modulation possibilities.

Setting Up the Audio-Sidechain #

On the bass track, I add the Audio-Sidechain modulator directly to the polysynth. The source of the modulation is the kick drum, which I route as the input for the sidechain. By pressing play and observing the VU meter, you can see the kick drum's signal being received by the sidechain device in real time.

Tuning Attack, Release, and Filter #

The Audio-Sidechain features controls that shape how it reacts:

• Rise (or Attack): Determines how quickly the modulation signal reacts to the incoming audio, in this case, the kick.
• Band Pass Filter: Here, I focus the sidechain’s effect on the frequencies where the energy of the kick is most prominent (the "meat" of the kick). By adjusting and visually inspecting the filter’s focus, I ensure the sidechain responds best to the strongest part of the kick.

Applying Sidechain Modulation #

By assigning the sidechain as a modulation source for the bass sound, you get classic sidechain compression, each kick hit dynamically reduces the polysynth’s volume. This pumping effect helps the kick "cut through" the mix while keeping the bass lively.

Beyond Basic Volume Ducking #

What makes the Audio-Sidechain especially valuable is its versatility. While many use sidechain simply for ducking the volume, I demonstrate that you can assign the sidechain to modulate other parameters, such as the synthesizer’s filter cutoff. This opens up countless creative options for rhythmically animated textures, not just static volume changes.

Using the Bass Sound as a Source #

To expand on the concept, I show how the Audio-Sidechain can also use the bass’s own output as a modulation source. By routing the bass signal back into the sidechain modulator, I can sculpt the bass sound based on its own dynamics, not just external sources. Focusing the filter on the lower frequencies provides a different, subtler modulation character compared to using the kick drum.

Audio-Sidechain as a Creative Tool #

The key takeaway is that Audio-Sidechain modulation is much more than a utility for mixing. It’s a flexible modulation tool that lets you react to any audio waveform and use it to control nearly any parameter within your synth or effect chain. This can bring more life and movement to your productions, making sounds feel more integrated and expressive.

Summary of Concepts #

Sidechain Modulation:
A process where the dynamics of one audio signal automatically control a parameter on another, or the same, audio signal.

Attack/Rise:
How quickly the modulation follows the input signal’s envelope.

Band Pass Filtering:
Isolating frequency bands of interest for focused sidechain reactions.

Beyond Ducking:
While often used just to lower volume during kicks, sidechaining can modulate any parameter, opening up more nuanced and creative sound design.

Conclusion #

I encourage experimenting with sidechain modulation throughout your projects, not just for volume ducking, but also for creative modulation of filters, effects, or any synthesizer parameter. This approach can transform the character and movement of your music, making your sounds more intricate and exciting.

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.