Tags: posts polarity-music OpenSource VST-Plugin Filters

Filt-R - The Free & Open-Source Filter Shaper Plugin

Tutorial | Jun 04, 2025

In this video, I explore Filt-R, a free and open-source filter plugin by the creator of gate 12 and time 12, which lets you automate both filter cutoff and resonance using envelopes and different filter models like Moog, MS-20, and phaser. I demonstrate how to shape filter movement and resonance over time, sequence envelopes visually with the waveform background, and show how useful this is for creative sound design, especially for basslines in Bitwig. If you’re interested, you can download it for free from GitHub (link in the description), and I’d love to hear your thoughts in the comments!

You can watch the Video on Youtube

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Summary

Maybe you don't watch the video, here are some important takeaways:

Hey everyone, welcome back! Today, I’m excited to talk about a new plugin called Filt-R, created by the same developer behind Gate 12, Time 12 and RipplerX. The concept of Filt-R is similar to those previous plugins, but with a key difference, here, I can modulate both the filter frequency and the resonance over time using independent envelopes. As I demonstrated, you can slide envelopes in the background and see exactly how the filter and resonance change in real-time.

Most of the controls and workflow are pretty familiar if you’ve tried the other plugins from this developer. There are a variety of synchronization options: I can trigger the envelope either with incoming audio or via MIDI, which lets me re-trigger everything precisely when I want. Patterns can be selected, and some global knobs allow me to manipulate the final sound or sequencing outcome.

Another cool feature is that Filt-R comes with various classic filter models built-in. The options include Linear, Sallen-Key, Moog, 303, MS-20, and even a Phaser mode, so there’s a lot of flexibility in shaping the tone. There’s also a built-in sequencer for drawing in the envelopes. Like the developer’s other plugins, Filt-R is 100% free and open source, you can head straight to the GitHub page, grab a prebuilt binary, or download the source and build it yourself. If you feel like supporting the project, there’s also an option to donate and help keep development alive. (You’ll find the link in the description.)

For today’s demo, I quickly loaded Filt-R into Bitwig. I used a detuned saw waveform alongside a drum loop and wanted to add a really fat filter to the bass. I specifically used the MS-20 filter model in bandpass mode, this is my favorite for big, edgy bass sounds. Once I soloed the bass, it brought back memories of those old Russian “optical basslines” from the '90s, super cool vibe.

Next, I played around with the timing of the envelopes, setting them to two bars so I could paint in nice, evolving filter shapes. I especially love that Filt-R shows the audio waveform in the background, which makes it really easy to see exactly where your envelope will affect the signal. You can snap envelopes to the grid, and there are offset controls for both the cutoff and resonance. When adjusting the filter shape, you can use attack and release controls to smooth things out or create really snappy, precise modulation.

Jumping between patterns, I explored Filt-R’s built-in sequencer, for example, I set the grid to six triplets for some patterns, then switched to 12, then back to eighth notes and sixteenths, building up some more complex movements. One thing I noted is how the global cutoff knob shifts the entire envelope curve up or down, giving you broad control over the filter’s range.

I also deep-dived into the phaser modes, using a spectrum analyzer to visualize the actual curve of each filter type. For example, Phaser mode shows up as two notches, while some filters offer a traditional lowpass or highpass shape. Switching between Linear, Moog, and MS-20, you can see subtle differences in their coloration. The plugin’s interface makes it easy to compare and tweak in real time.

The key takeaway for me is how easy and visual it is to design envelopes in Filt-R. Unlike Bitwig’s own automation or curve modulators, which don’t show the waveform in the background, and often smooth out sharp edges, Filt-R lets me work with much greater precision. I can draw exact shapes and immediately see their effect, which is something I often miss in other workflows.

Overall, since Filt-R is open source and entirely free, there’s really no reason not to try it out. The sound quality is fantastic, especially for acid or modern basslines, and the interface is super intuitive if you care about envelope-based sound design. If you want to grab it, check out the link in the video description!

So that’s it for today’s video, I hope you enjoyed this look at Filt-R. Please leave a like, subscribe, and let me know your thoughts in the comments below. Thanks for watching, and until next time, bye!

Transcription

This is what im talking about in this video. The text is transcribed by AI, 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.

[00:00:00] Hey folks, welcome back. Today it's about Filt-R by the same guy who made gate-12 and time-12.
[00:00:06] It's kind of the same concept except here we can change the filter frequency over time with an
[00:00:12] envelope and also the resonance with a different envelope as you can see here sliding the background.
[00:00:17] The rest is kind of the same thing. We have different synchronization options here. We can
[00:00:24] trigger the envelope with incoming audio or with a MIDI, you know, just to re-trigger the whole
[00:00:30] thing. We have different patterns here. We have also some global knobs. We can change the outcome
[00:00:36] of the sequence here. We have also different filter types. We have here linear, Sallen-Key,
[00:00:43] Moog 303, MS-20 and Phaser. And yeah, a sequencer to sequence here the envelope and also this one
[00:00:54] is completely free as the rest of the plug-ins. It's open source. So you can just head over to
[00:01:00] the GitHub page and you can download your binary or maybe just download the source and build it for
[00:01:05] yourself and you maybe can also donate here a bit of money just to keep this project alive.
[00:01:13] The link is in the description below. Make sure you just download this because it's very dope.
[00:01:20] In Bitwig here I just use detuned saw waveform and drum loop.
[00:01:30] And I just want to put here a nice fit on it. So we use Filt-R. That's the name.
[00:01:37] Don't mistake it for "filtrr" which is kind of the same name but it's a different plug-in.
[00:01:47] So here we choose maybe the MS-20 mode because that's my favorite and we go for bandpass.
[00:01:58] So let's solo here the bass.
[00:02:04] It reminds me a bit of the old at-russian optical bass lines from the 90s.
[00:02:19] Yeah really nice. So we can change here the timing to maybe two bars
[00:02:35] and then we can see in the background here the audio waveform of course.
[00:02:44] And then just paint in here some maybe a navel snapping.
[00:02:48] And maybe change the resonance here also over time.
[00:03:04] Ah maybe a bit cut off here a bit higher.
[00:03:17] So there's an offset here so we can add a bit of offset and you can see
[00:03:27] the filter is now in a different place and we can also see this trail which helps you kind
[00:03:34] of see what's happening because when you dial in sometimes pretty edgy filter shapes or envelope
[00:03:44] shapes here like this we can then use attack and release to just smooth this out right.
[00:03:51] You can see here it's not going all the way up it's just a rounded curve.
[00:04:04] Ah really nice. Okay let's go to the third pattern here and we use the sequencer.
[00:04:20] So we can choose here grid let's say six triplet and then something rounded maybe here.
[00:04:29] And then we use grid 12.
[00:04:36] Maybe go to two bars again.
[00:04:42] Okay maybe in the beginning here we do something edgy for let's go here eight note.
[00:05:10] And then apply. Increase this a bit.
[00:05:22] Yeah the interesting part is that when you change the cutoff here the global cutoff
[00:05:33] it moves the whole envelope up.
[00:05:39] Maybe bring this up or it's actually snapping.
[00:05:45] Yeah it's snapping to the left that's disabled snapping here.
[00:06:01] That's also not right.
[00:06:10] Oh it's a different offset when you are on resonance here the offset is
[00:06:35] yeah that's the offset for the resonance okay I see.
[00:06:40] Okay let's try something different here let's go to four and maybe switch this to
[00:06:54] three or three here let's see all the sounds offset drive release let's bring this back.
[00:07:02] Let's use the sequencer again 16 notes let's paint this in.
[00:07:22] Okay.
[00:07:32] Yeah it's maybe good for asset baselines.
[00:08:02] Let's try out the phaser here. What I want to do is I want to check this here with the
[00:08:06] EQ curve analyzer so we can see how the filter actually looks like EQ curve analyzer.
[00:08:14] Okay so we have this maybe just completely reset it here filled R.
[00:08:28] Okay this is linear 12 let's go down it's the resonance let's go to three or three it looks
[00:08:37] like this okay it's deeper phaser yeah it's basically two notches here
[00:08:47] and filter phaser minus looks like this okay there's one notch and then a low pass and a high pass
[00:08:56] okay nice. Let's switch to analog 12.
[00:09:04] It's yeah you can't see the difference here there's probably some coloring happening somewhere
[00:09:13] it's the moque.
[00:09:19] Yeah okay so yeah that's the that's the filled R plug in kind of like it.
[00:09:26] I probably use it a lot because I like this the sound of the moque and the ms20 here for
[00:09:36] bass sounds and it's so easy to draw in the envelopes here right because you can see the
[00:09:41] waveform in the background and that's sometimes what I miss with the automation system here in
[00:09:47] bitwig right because you can't see where you paint something in at least here with the curves modulator
[00:09:54] you don't see anything in the background here you basically blind it and then you can choose the
[00:10:02] automation for that which is a bit better in in bitwig but then you have the smoothing applied
[00:10:08] right so when you paint in here pretty hard edges it doesn't work anymore it's rounded
[00:10:14] or it's smoothed out in bitwig at least so here it's precise if you want it to be if you wanted
[00:10:20] to have it precise and you can also see the waveform in the background so also it's completely free
[00:10:27] so why not right so the link is in the description below if you want to download this and that's
[00:10:33] it for this video thanks for watching leave a like leave a subscription and let me know what you
[00:10:38] you think in the comments down below, of course, right? Bye.