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Spectral Compressor - Sidechain Everything

Tutorial | Aug 12, 2025

In this video, I discuss how to use the free and open-source spectral compressor plugin in Bitwig for precise sidechaining and frequency ducking, especially when working with combined drum loops and bass tracks. I demonstrate how its audio-rate processing and flexible attack and release times make it uniquely effective for not just kick and bass, but also for managing overlapping frequencies in pads and leads, allowing for detailed mix control without needing separate drum tracks. While powerful, the plugin requires careful adjustment to avoid overly digital or unnatural results, and I encourage viewers to experiment and share their own use cases.

You can watch the Video on Youtube

Short Overview

In this video, I discuss how to use the free, open-source spectral compressor plugin for precise sidechain ducking and frequency shaping in Bitwig. I demonstrate different techniques for sidechaining bass to a drum loop, including using the spectral compressor to dynamically duck specific frequencies at audio rate for ultra-clean mixes. I share practical tips on attack and release settings, and explain how you can use the plugin not just on bass and drums, but also creatively on pads and leads to make space in your mix. This approach helps achieve a polished sound without needing to split drum tracks or overcomplicate routing.

Apology for Previous Audio Issues

In my previous video, the background music was a bit too loud, and while I personally did not find it too distracting, I received feedback that it made things harder to follow. In response, I have removed background music from this video to make everything I say perfectly clear.

Introduction to the Spectral Compressor

Today I want to talk about a plugin that many producers already know. It is free, open source, and has been around for a while. I previously created a video about it back in 2023. Sometimes it takes a while to fully appreciate a tool and discover optimal use cases for it. The spectral compressor is one of those plugins that, once understood, can become an essential part of your workflow.

Example Using Drum and Bass

To illustrate its use, I set up a drum and bass track featuring a combined drum loop (kick, snare, and hi-hats together) and a bass sound. The kick and bass occupy some overlapping frequencies, especially in the low end. Normally, you would separate the kick drum from other elements in the drum loop so you can sidechain the bass precisely, using the kick as a trigger for sidechain compression. However, when using a combined audio loop with no individual triggers or MIDI tracks, traditional sidechain methods become impossible.

Understanding Sidechain Compression

Traditional Sidechain Compression

Sidechain compression is a production technique where the volume of one sound is dynamically reduced in response to another sound. This is often used in electronic music to make space for the kick drum by reducing the volume of the bass or other elements when the kick hits. Ideally, this is triggered by a clean kick drum track to achieve accurate and controlled ducking.

Audio Sidechain Solution

When only the full drum loop is available, you can use an "audio sidechain" rather than a MIDI-triggered sidechain. This approach takes the entire drum loop's audio as the sidechain input and allows you to focus on specific frequency ranges, such as just the low end where the kick sits.

Why Use a Spectral Compressor?

The spectral compressor operates differently from standard broadband compressors. Instead of compressing the whole signal, it works on individual frequency bins, making it possible to duck only the frequencies present in the sidechain input. This results in more precise and transparent ducking, particularly useful in complex mixes where elements share frequency ranges.

Applying the Spectral Compressor in Bitwig

You can use the spectral compressor in Bitwig by routing the entire drum loop as a sidechain input to the bass track. By switching the compressor to "sidechain matching" or "sidechain compression" mode, the plugin only reduces frequencies present in the drum loop from the bass. One key benefit is that the compressor can respond not just to kick but also to snare and hi-hats, handling overlapping issues not just in the low end but across the spectrum.

Audio Rate Processing With Zero Attack and Release

One unique characteristic of this spectral compressor is its ability to operate at audio rate by setting attack and release times to zero milliseconds. This allows it to respond to every little peak and tail in the audio, providing extremely accurate and fast ducking. For more natural results, you can adjust the global threshold or use a very short release time to smooth out the effect.

Fine-Tuning the Compression

The plugin offers different options to adjust how frequencies are compressed. You can use slopes such as pink noise or white noise, or customize the curve. This allows you to target only the sub frequencies with the kick or broaden the compression to cover more of the spectrum, including the snare and hi-hat ranges. The threshold and ratio controls help define how much reduction is applied.

Use Cases Beyond Drums and Bass

Although sidechaining between kick and bass is a classic application, the spectral compressor excels in other scenarios. For example, you can use it on pads or leads that compete for frequency space. By sidechaining one pad to another or to a lead, you can create space for important elements in your mix, pushing some sounds into the background and letting others shine.

Multiple Instances and Hierarchical Mixing

The low CPU usage of the spectral compressor means you can use multiple instances in one project. This enables creative possibilities such as hierarchical mixing, where background elements automatically make space for foreground sounds. You can establish a structure in your mix where less important tracks yield to more important ones based on the song's needs.

Potential Pitfalls

Because of its precision and power, the spectral compressor can easily be overused. Long release times or extreme settings can completely remove important elements from your mix, creating unnatural frequency holes or a harsh, digital sound. It is important to use it with intention and moderate settings for best results.

Similarities to Trackspacer

The spectral compressor can be used in a similar way to the plugin Trackspacer, but with the added benefit of audio-rate response and highly detailed spectral control. It is particularly powerful as a spectral dynamics tool for ducking unwanted frequencies and creating space in a busy mix.

Final Thoughts

Mastering the spectral compressor takes some experimentation, but once you do, it becomes an invaluable tool for sidechaining, frequency carving, and dynamic spectral shaping. I use it all the time for ducking, masking issues, and balancing elements in dense arrangements. It is especially effective in electronic music genres like drum and bass but also works well on pads, leads, and other layered sounds.

If you have experiences or tips on using the spectral compressor, feel free to share them. I hope this video has improved the audio quality and helped you see new ways to use this powerful plugin.

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] Hey guys, welcome back. So in the last video, the background music was a bit too loud.
[00:00:03] Sorry for that. In my opinion, it wasn't that bad.
[00:00:07] My mean, you could hear everything I was saying, but you know, people complain.
[00:00:11] So this time, no background music so you can hear everything I'm saying.
[00:00:15] So today I want to talk about the plug in that everyone knows it's free.
[00:00:20] It's open source. It's around for some time.
[00:00:22] And I also made a video about it back in 2023.
[00:00:27] So a long time ago and sometimes it takes a bit of time
[00:00:31] until you get used to the plug in and how to use it and what kind of situations
[00:00:37] and, you know, how to utilize it in a certain range
[00:00:41] that you actually accept or that you like.
[00:00:43] So the spectral compressor is completely free.
[00:00:46] I put a link in the description below and I show you here an example.
[00:00:50] So in the background, I have some kind of drum based tune.
[00:00:52] So let's listen to that.
[00:00:55] So drum base and a bit of funk or funky drum base, however you want to call it.
[00:01:12] So the problem here, it's actually not the problem,
[00:01:15] but here the situation is we have a drum loop and the drum loop is a combined
[00:01:19] drum hit track. So we have a kick drum, we have a snare and we have hi-hats in there.
[00:01:23] So it's combined and we have a bass sound here, right?
[00:01:27] The bass sound or the sub shares some frequencies with the kick drum.
[00:01:31] So you can see this also here, that's the kick drum.
[00:01:34] So lots, lots of low end there and also the bass.
[00:01:40] So right, it doubles in basically the frequency.
[00:01:49] And what you want to do is you want to side chain the bass to the drum loop here.
[00:01:55] And usually what you do is you just separate the kick drums from the snare drum.
[00:02:00] So you have a separate kick drum track and then you can use this kick drum track
[00:02:04] to trigger actually the side chaining on the bass.
[00:02:07] That's what you usually do to get actually precise side chain.
[00:02:11] And we can also do this here in Bitwig.
[00:02:14] We can just put a tool device here on it.
[00:02:19] And you can't use the note side chain here, of course.
[00:02:22] This one, because it needs a MIDI track or a note track as an input
[00:02:27] to trigger actually this envelope and then we pull down the volume.
[00:02:31] So this is not possible because this is a drum loop, it's an audio track.
[00:02:35] So there are no MIDI triggers or note triggers on that.
[00:02:38] So we can use here a different one.
[00:02:42] We can use the audio side chain.
[00:02:47] With this, we can just feed in the whole audio track of the of the drums here.
[00:02:54] And then we can say we want to focus, let's bring this down here for a moment.
[00:02:59] We want to focus only on the kick drum down here, right?
[00:03:02] And then we get here the trigger signal.
[00:03:05] And you can see it's a slightly slightly curve here in the beginning, a slope.
[00:03:12] And that's because because the kick drum has some upper tones.
[00:03:18] It has a pitch drop, right?
[00:03:20] It starts at the top of the pitch and then it goes slowly down.
[00:03:23] And so the sub is not in the beginning in the tech phase of the kick drum.
[00:03:27] There is no sub, the sub comes later.
[00:03:29] So this is why you have this slope here.
[00:03:33] Which is completely fine.
[00:03:36] And because you only want to side chain basically the sub of the kick.
[00:03:40] So when in the beginning of the kick drum there is no sub.
[00:03:43] You don't need to side chain, basically.
[00:03:45] So this would be completely fine here.
[00:03:48] So just pull down the volume here.
[00:03:52] Let's actually put here some kind of what's the name Oscope.
[00:04:05] I used Oscope here for some reason.
[00:04:08] Right, you can see how the base goes down here.
[00:04:16] This is the kick drum.
[00:04:17] Basically, we can also bring in here the kick drum or the drum loop drum base post.
[00:04:23] Right, you can see here is the kick drum.
[00:04:32] And this is here the base, which is stuck in the beginning.
[00:04:34] Here we have this small little portion.
[00:04:37] And some people believe that this needs to be cut out because it's not clean or anything like this.
[00:04:43] But what you see here is actually not the sub frequencies.
[00:04:46] It's just the pitch drop, the beginning of the pitch drop, right?
[00:04:50] So the kick drum here in the beginning has upper frequencies.
[00:04:54] And then it goes in the pitch drop and then you have the sub here.
[00:04:56] So here's the sub part.
[00:04:58] So this is what you need to side chain actually.
[00:05:00] So this is not unclean.
[00:05:01] It's just, you know, it's just the attack phase or the pitch drop of the kick drum.
[00:05:06] So it's not bad in my opinion as we can leave this in.
[00:05:09] But that's not what I want to talk about.
[00:05:12] I want to say that this is here okay to do in Bitwig.
[00:05:17] But we can also just use here the spectral compressor.
[00:05:21] This one, so this one works a bit differently.
[00:05:28] So it takes also a side chain input.
[00:05:31] Let's go here, side chain input and we use the full drum loop here.
[00:05:36] And we switch here in the spectral compressor to from pink noise to side
[00:05:41] chain matching to side chain compression.
[00:05:44] So now it takes the drum loop as an input
[00:05:47] and tries to duck the frequencies of the drum loop here inside of the base.
[00:05:52] So the benefit of this is that you also get with this
[00:05:56] a side chain for the snare and the hi-hat.
[00:05:59] And I kind of find this appealing for some reason
[00:06:04] because sometimes I have in drum base, I have a lot of overtones.
[00:06:08] So I have a sub base, right?
[00:06:10] I have overtones and then I have sometimes some fizzle on top.
[00:06:13] And you also get into problems when you have the hi-hat
[00:06:17] kind of masking what the fizzle of the base does or vice versa.
[00:06:25] So you also want the side chain there for some reason.
[00:06:28] So I really like to just use your attack 0ms and release 0ms.
[00:06:34] And that's also a very special thing about the spectral compressor.
[00:06:37] You can use 0ms for attack and release, which makes this working at audio rate.
[00:06:44] So every little tail or peak of the kick drum,
[00:06:49] you know, every little wave thing here is used to duck actually the base.
[00:06:58] And this makes it very precise for some reason.
[00:07:01] So here we pull down the ratio to 500 to 1 for downwards compression.
[00:07:08] And then maybe we can play around with a global threshold.
[00:07:11] You can see here the kick drum completely removes the base, right?
[00:07:17] If I just disable the CFO moment, you can see here it's there.
[00:07:24] So when I enable the spectral compressor.
[00:07:26] So let's bypass this.
[00:07:37] So as you can see, we duck here at the base now with the kick drum,
[00:07:50] with the snare drum and with the hi-hat.
[00:07:53] And I kind of overdo this here a bit with the threshold.
[00:07:57] So we don't need to do this dead drastic.
[00:08:00] You can also play around with the release time.
[00:08:02] And then you can hear the effect a bit better.
[00:08:04] And it sounds like this because the release time is much longer
[00:08:20] than the kick drum sample or the snare drum envelope
[00:08:24] or the kick drum envelope and the snare drum envelope, right?
[00:08:27] So the ducking is much longer than the sound itself.
[00:08:30] So we basically create some kind of frequency hole
[00:08:34] where the kick drum is much longer than the kick drum actually is.
[00:08:37] So there's a hole with nothing to fill basically.
[00:08:42] So that's why I like to have the release time pretty slow.
[00:08:47] So usually kick drums in drum bass for me are around 88 milliseconds long, right?
[00:08:53] This is a 16 note by when you have one at the BPM 16 note is around 88 ms.
[00:09:02] And an eight note is around 170, 80 ms around that time.
[00:09:10] So usually using this here very, very fast release time makes it for me.
[00:09:18] So this is audio rate.
[00:09:20] And then you can kind of create some slew or lag here with this
[00:09:25] and make it a bit more smooth.
[00:09:27] So I use very short release times in the very fast or zero ms attack time here for the ducking.
[00:09:34] And then I play around here with the global threshold.
[00:09:38] So if you don't like that here, the snare drum and the hi-hats are ducking the bass,
[00:09:43] we can also play around here with the threshold slope over the curve.
[00:09:46] At the moment we have it here at pink noise, 3 dB per octave.
[00:09:50] So we can make this pretty straight, which is white noise or even do something like this.
[00:09:56] And then we can go up here with the global threshold.
[00:10:00] You can see only the kick drum here is basically used to pull down the lowest sub.
[00:10:06] So what I want to say is this spectral compressor is very fast.
[00:10:20] It works at audio rate speed.
[00:10:22] So you can make very precise frequency cuts.
[00:10:27] And it's very well made for ducking frequencies, in my opinion, not only to just compress.
[00:10:36] So I use this for ducking all the time.
[00:10:39] And not only for kick and snare and bass sounds, I also use this on pads sometimes.
[00:10:46] So I have one pad and then I have another pad playing in the same frequency range.
[00:10:51] And I put this on here with audio rate speed and then they kind of cancel each other out.
[00:10:56] Or maybe one lead sound makes room on the other pad sound.
[00:11:00] And it works very well, actually.
[00:11:03] You can kind of destroy the sound if you use it here in a duetrastic way.
[00:11:13] But as I did here right with the release time here, it doesn't make any sense.
[00:11:19] Right, so with this, we basically completely eliminated the sub and it never placed the sub
[00:11:31] because the release time is much, much longer than actually from one kick to the other kick.
[00:11:37] So you can destroy the sound if you don't pay attention what you actually do with this.
[00:11:44] But I really like the spectral compressor.
[00:11:46] It's very raw as we have to know what you do, like with most things, I guess.
[00:11:53] But I use it all the time lately for all kinds of ducking or removing frequencies
[00:12:00] or like people use to have this, what's the plug-in track spacer.
[00:12:05] So yeah, I use it basically like track spacer.
[00:12:09] But this one here is rocking at audio rate and it's on a spectral base.
[00:12:14] So it's a spectral dynamics tool, more or less.
[00:12:17] That's what I want to show you basically.
[00:12:21] Maybe I give you an example also for pad sounds here.
[00:12:24] Maybe that style is in here first for them.
[00:12:32] Sounds too drastic.
[00:12:36] What you also can do is you can use upwards compression here to bring up some frequencies
[00:12:51] in the bass that are not there.
[00:12:52] So you can make an EQ boost.
[00:12:54] Not too much.
[00:13:09] Not too much.
[00:13:09] Uploads compression can make it sound very, very destroyed, very fast.
[00:13:15] But it's possible.
[00:13:17] So here's another example.
[00:13:18] I have a lot of pad sounds or a lot of lead sounds playing together.
[00:13:22] So I take the pad sound here and I put the spectral compressor on it.
[00:13:35] And I use this as a sidechain input here, of course, the synth lead.
[00:13:40] So the second track.
[00:13:41] I put this here into sidechain compression mode and a bit of slow attack, slow release.
[00:13:47] So the pad sound makes room only where this sound is playing and only the
[00:14:08] needed frequencies.
[00:14:10] So it's very precise and it only takes the frequencies away.
[00:14:14] You are actually all playing on the second sidechain input track.
[00:14:18] You can even use the spectral compressor with a lot of multiple instances.
[00:14:25] So because this is very light on the CPU, you can say, oh, I have actually here a synth lead,
[00:14:31] but I also hear a second pad sound playing.
[00:14:34] Or maybe here.
[00:14:39] So I want to also make room for this sound.
[00:14:45] So I use a second spectral compressor.
[00:14:47] I can use also different settings.
[00:14:51] So here, pad 2 post, sidechain and also a bit of ratio here.
[00:15:14] So in this example, we just could use this here inside of a group and then use the group as a
[00:15:20] sidechain input.
[00:15:21] But I want to give you basically this example that you can use it in multiple combinations.
[00:15:26] So here it's more like an hierarchy.
[00:15:29] I say the pads are actually only for the background.
[00:15:32] I want to have this in the background and fill up some space.
[00:15:35] And the sounds coming in here, the synth lead or the pad 2 are actually more important at this
[00:15:41] point in time.
[00:15:42] So please pads make some room for these sounds.
[00:15:47] So this is what I'm saying.
[00:15:49] So I can build up here some kind of hierarchy to my track.
[00:15:56] I say this is not important.
[00:15:58] It's just in the background to fill up some space.
[00:16:01] And when there is something in the foreground, please make some room.
[00:16:05] And I can use this here in multiple combinations.
[00:16:08] I can also say here also make room for the bass or for the drums.
[00:16:12] And sometimes I put these into different groups and then I use the groups as a sidechain input.
[00:16:18] Just how your track needs it at the moment.
[00:16:23] Here in this example, I don't need any spectral compression at all.
[00:16:27] It's not needed for this kind of track.
[00:16:30] Just as an example that you can use it actually on pad sounds.
[00:16:33] But here in this example, it's not really needed.
[00:16:36] But it also doesn't do any harm.
[00:16:40] So here I'm using it on the drums.
[00:16:50] Same thing.
[00:16:51] I have the drums here more or less as one group.
[00:16:53] And yeah, I don't want to separate.
[00:16:58] I don't want to have a separate kick drum track and a snare drum track just so I can
[00:17:05] grab the sound or the audio to trigger a sidechain.
[00:17:08] So here I can have everything combined.
[00:17:11] And then I use the spectral compressor on it to just duck the right frequencies.
[00:17:17] So that's how I use it.
[00:17:18] I want to show you this.
[00:17:21] I know you probably already know it.
[00:17:23] And there are a lot of tutorials out there showing you this.
[00:17:26] But that's how I use it.
[00:17:28] And it took some time for me to actually find the real nice use case for this plugin
[00:17:33] because it's so raw and you can do so much damage so quickly.
[00:17:37] And it sounds very spectral, ish, very fast.
[00:17:42] So there's no kind of oh, please combine multiple frequency bins into one like in DSQ3.
[00:17:48] Here you have really every single bin separate.
[00:17:54] And if you don't pay attention, it sounds very digital, very fast.
[00:18:01] That's what I want to say.
[00:18:02] That's for this video.
[00:18:04] Please leave a like, leave a subscription.
[00:18:06] Let me know what you think.
[00:18:07] How do you use the spectral compressor would be interested in that.
[00:18:10] Let me know in the comments.
[00:18:11] And I hope the audio is not that loud this time.
[00:18:15] And I see you in the next video.
[00:18:18] Bye.