1950s Filter


Rysy is a faithful recreation of a legendary filter and a tube preamp, famously used by Karlheinz Stockhausen, the Polish Radio’s Experimental Studio and other pioneers of electronic music. And now - you.

+ VAT depending on region. Discounts?

The legend

The year is 1957. In a small country in the Eastern Europe, a new music studio is opened. In a few years, it becomes a symbol of artistic freedom, unheard-of in the communist block. It also just happens to be one of the very first experimental music studios in the world. They even make dub techno there, before it’s recognized as a genre.

This is the Polish Radio’s Experimental Studio. It closes in 2014, after half a century of pushing the boundary of sound exploration.

This is where this filter came from. And I mean this both literally and philosophically.
Designed for creative sound shaping, the legendary W49 Hörspielverzerrer consists of two filter bands - a low pass and a high pass - and an intensity control, which changes the response of the unit. It ranges from brutal to almost subtle. It’s a sound design instrument in its own right.

Even running the sound through the filter with all controls set flat will add a new dimension to your tracks. Especially since the filter is designed to work with an extremely rare V41 tube preamp (predecessor to the more popular but not as nice sounding V72), which the plugin captures faithfully. And yes, I have two in the studio.

The plugin

Filter bands
Shape your sound with characterful lowpass and highpass filters.

Alter the filter response with a smoothly automate-able intensity knob.

Instantly add rhythmic interest with the built-in LFO, wired to the intensity knob. The LFO speed is unsynced to honor the experimental nature of the filter.

Introduce authentic, analogue noise sampled from the real hardware. Because digital is too clean.

Rysy in context

Watch Rysy processing a wide range of tracks, submitted by the Felt community.

Hear it yourself

See how Rysy compares to the unit that inspired it as both are used to process an awesome beat by Joshua Van Tassel.


Watch Snakes Of Russia shape Helenko pads using Rysy: it’s really great at carving out some space for sounds that take up a lot of room in your mix, while at the same time giving them some character.


Watch Jogging House as he explores Rysy: I'm using several instances of Rysy to drastically restrict the frequency range of sounds, add color and create movement via its LFO.


Watch OORA add motion to Helenko pads using Rysy: I love how the result is organic and melancholic. Also using the cxm1978 as external reverb to glue it all.

Legacy of the Polish Radio’s Experimental Studio

Rysy was born out of fascination in the experimental techniques and tools used at the Polish Radio’s Experimental Studio, where repurposed measurement equipment clashed with creative tape editing, groundbreaking sonic explorations and a belief that paths are to be set, rather than followed.

I’m extremely proud to bring these tools to light and share them with the next generation of music producers. Put your explorer hat on. Dare to change things.

fot. Andrzej Zborski/FOTONOVA

What makes it different?

While most filters on the market emulate three of the most popular synthesizer filters, Rysy takes a different approach. It captures an extremely rare (up to a point of being unobtanium) filter created in the 1950s and used in the most famous electro-acoustic music studios of the time.

However, it’s not only the sound that’s unique. The filter bands are stepped and are not really meant to be automated (turning the knobs creates a short period of silence), so you can’t sweep them like on your standard synth. Some of you might see it as a limitation, but it’s something that forces you to approach things differently. You might set your cutoff points first and then animate things with the Intensity knob. Or find your own way around it. After all - it’s the explorer’s filter. Don’t approach it like something that’s supposed to be standard.

So, long story short - it’s not yet another filter to sweep your phat sawtooth with. And it’s got vibe for days.

And in the true Felt spirit, you can dial in some tasty noise for that authentic analogue vibe. And yes, the noise is sampled from the hardware.


VST / AU / AAX plugin for Windows and macOS (10.11 or newer). Lifetime free updates. Watermarked to you. Downloads with Pulse.

8GB of RAM and an i5 or better CPU required. A modern computer highly recommended.

The plugin supports every major DAW like Ableton, Logic, Pro Tools, Cubase, FL Studio, Studio One, Reaper etc. Mac and Pro Tools versions 64-bit only.


Variable bandpass filter with 11 stepped frequency cutoff points per band

Faithful emulation of an extremely rare stepped filter and an equally rare tube preamp.

+ VAT depending on region. Discounts?

With great power comes great responsibility. Due to its cutting-edge sound (no pun intended!), the plugin may be CPU intensive, depending on your system configuration. Also, as with the real hardware unit, there’s a short interruption as the high and lowpass filters are adjusted. If using very fast Intensity automations, you might need to bounce in non-realtime mode.