VST synth, “Microtonal Poly Worms” v2.1 – has 5374 tunings (!), 64 presets. Polyphonic, microtonal, free, easy to use, robust.


Get it from the listing on KVR Audio, here.

or DOWNLOAD IT here. MicrotonalPolyWorms Version 2.1 (9.6 megs)

This works on 64-bit Reaper, and on some other 64-bit DAWs.  But also try try our 64-bit-only VSTs. 64-bit “Simple Microtonal Synth” and Simple Microtonal Sampler, 64-bit Windows, v1.0.

(Check our new record that uses this synth extensively. Free to listen or download: Microtonal Cats from Alpha-Centauri)

YouTube walk through of this VST

Note: if you want to use this synth non-microtonal, use the Tuning setting of 12 EDO.

Other VSTs we make, including some microtonal

(Check out my other microtonal music.)

Microtonal Poly Worms

is a free polyphonic VST microtonal Windows synth from Michael W. Dean of BipTunia.

This is the easiest microtonal synth to use.

Yet it is robust, and will give you power.

Microtonal Poly Worms is a no-nonsense introduction to microtonal synthesis, It’s great for heavy bass, forceful leads, crystalline chimes, and more.

Microtonal Poly Worms is fun, polyphonic, and is truly microtonal. So you can enjoy non-standard (for the West in the current year) scales and tonalities going back thousands of years, from all over the world. It also includes new tunings from the future that are the product of maths and art mating in the minds of some very smart and creative people.

Enjoy it. And tell two friends! Spread xenharmonic joy!

MicrotonalPolyWorms has 32 notes of polyphony, yet very low memory usage. It also holds its scale setting in a project when you close and reopen your DAW. Not all microtonal synths do.

TO USE: Unzip and put the folder \MicrotonalPolyWorms inside your DAW’s VST folder.

System Requirements:

Microtonal Poly Worms is a 32-bit Windows synth, but it tested fine on 64-bit Reaper, and of course also on 32-bit Reaper. And tested as working well on Cubase, both 32-bit and 64-bit.  It should work on any 32-bit DAW, and on many 64-bit DAWs. Though in 64-bit Reaper, the presets will show up in a second window, like this:

(^ If the window on the right isn’t wide enough to see all the preset names, you can grab either side of it with your mouse, hold down the left  mouse button, and drag the window wider.)

If you can’t even see the main colorful window with the gummy worms, click the button on the VST picker that says “Show UI” (user interface):



(At bottom of page are directions for adding a VST in Reaper.)

GETTING TO KNOW MicrotonalPolyWorms

SO…This version has 64 presets, and 5089 tunings (scale files, in MTS format).

Each preset has a different tuning, but you can use the picker to add any of the tunings to any of the presets. You can also make your own synth patches, or add your own tunings (in MTS file format, put into the \MicrotonalPolyWorms folder inside your VST folder).

The order of MTS files in the presets are set up somewhat randomly, to encourage experimentation. But you can stop using the set tunings in a given preset at any time, and pick your own. You do this by clicking on the file picker near the bottom right, on the “CHOOSE MTS TUNING FILES” section at the bottom, and picking any of the other 5089 scales.

The archive also includes Sevish’s PDFs about many of the tunings, included at his suggestion. They are a great read. Very educational, but not at all dry.

(Check out Sevish’s Resources for Microtonal Musicians page.)

If you read about a tuning you like and want to try it, you can click the file picker icon in the bottom right of the User Interface, circled here in blue:

This will open up the list of tuning MTS files. From there you will have a search function where you can type the name. It will bring up your results:


From there, click on the file icon to use the scale. (Where it says “Eagle53” in the above image. But it will be replaced by the name you searched.)

Tip: If you want to play in typical western 12-tone equal temperament, pick this scale:

12 TET.mid

MicrotonalPolyWorms has a couple of cool frequency meters, and a MIDI control readout. These are diagnostic tools used while making a VST, but usually removed before outputting for the public. I like ‘em, so left them in. They’re stoney and groovy. But they also teach you a bit about how this all works, and what audio synthesis actually is.

You can also use them to see different harmonics (the different peaks shown below in the blue meter on the left).

The meter on the left shows a logarithmic frequency scale.

The meter on the right shows a linear frequency scale;

The mod wheel function on MicrotonalPolyWorms is unique. It controls a combination of sustain, phase mod, and pulse width. It’s somewhat more subtle than many expect from a usual mod wheel, but very useful in creating a shimmer or very special vibrato by hand.

The mod wheel will do more on some presets and patches than on others. And will do more in some octaves than on others.

We recommend you try patches and tunings you like in different octaves as well. And with single notes, two- and three-note chords, and also try chords with more notes.

This synth will also produce very interesting results with an arpeggiator. Try it!

The pitch wheel on your MIDI controller will control pitch. The amount you can bend with it is different on some presets, and can be changed manually with the “Bendy Worms” switch.


Enjoy, and please tell two friends.

If you want to donate, there are links on the left sidebar for patreon, Bitcoin, and PayPal. Or you can buy one of my albums for you or a friend, on BandCamp, or any of these services:

VST ID of MicrotonalPolyWorms is MtPW

Check out our other free VSTs here.

Check out my microtonal  music here.


Jef McClintock showed me how to add the microtonal function. (Though I simplified it.) Thank you, Jef!

And thanks to Nora Leader for helping me get rid of the errors in file picking the MTS files.

The scale files for the tunings came from these three sources; Scala archiveXen-ArtsSevish. Thank you.

I made the scale 120 EDO.

Thank you to Manuel from Scala for help on how to convert his 4000 .scl files to .mts files.

Jay from Nowhere helped with some of the early work on this (on LuckyWorm, the non- microtonal non-polyphonic synth I previously made, that I adapted this synth from).

Microtonal Poly Worms was made with SynthEdit.

Microtonal Poly Worms controls:
The two oscillators are called “worm food” and “worm poo.”
“slime” is filter resonance.
“goo” is other filter resonance.
“worm hole depth” takes one oscillator slightly out of tune for depth. This is something you’ll want to use lightly, if at all, until you get used to the sounds of the scales…as it will hide the unique nature of each scale.
“There are two un-labeled frequency analyzers. Left one is a logarithmic frequency scale. The right one is a linear frequency scale.
“voodoo” shows fun MIDI numbers and voltages.
“ASDR” is obviously the envelope.
“worm gas” is an ASDR filter
“breed worms” is speed of delay.
“feed worms” is feedback of delay.
“bendy worms” is amount of pitch on pitch wheel. Will respond in 12 TET (a.k.a. 12 EDO, that is, normal western standard tuning) amounts, not in the intervals of the scale you’re using. Though you can play microtones manually with the pitch wheel.
The unnamed switch next to the unnamed LED is TurboWorms.

TurboWorms turns the synth up a little too loud. This can make a sort of “overdriven” sound with extra harmonics, like a loud guitar amp.

“Number of worms” is output volume. I recommend you turn this down before turning on the TurboWorms switch.


Worm Out of It
Brain Worms
Bad Brain Worms
Base Worms
Hell is for Worms
Worm Horn
The Worm Has Turned
Down the Worm Hole
Do Da Worm
Early Bird
Michael Wormham Dean
Worm Food
Disco Wurm
Lucky Worm He Was
World Wide Worms
Hooked Worm
W.W. Wormsworth
Hook Me Up With Worms
Your Wormness
WYO Worm Bell
WYO Worm Belle
You Have Worms
Inch Worm
Rain Worms
April Worms
Hail Worms
Lead Worms
Permanent Worms
End of the Worm
Eagle Eat Worm
Eagle Calliope
Lucy in the Sky w/ Worms
I Love Lucy 22
Lucy’s Car Horn
Lucy Turns 19
Gradus Generation
Studly Worms
Bag O’ Worms
Harmonic Worms
Bratty Worm
Tetragram Sam
23 Worm Skidoo
Young Worms
Yekta Worms
Magic Worms
Elf Worms
Tree Worms
Mbira Worm
Juicy Worms
Non-8 Worms
Can O’ Wormz
Night Crawler
Feature Not Bug
Worm’s Eye View
Rat Worm
Fishing Rod
Rod Man
120 EDO Worms
120 EDO Shimmer
120 EDO Chime

LEGAL:  VST® is a trademark of Steinberg Media Technologies GmbH, registered in Europe and other countries.

Michael W. Dean has been licensed for VST SDK use by Steinberg. Agreement countersigned by Steinberg on August 23, 2018.


Download and unzip. Put the unzipped MicrotonalPolyWorms folder in your VST folder.

Then open Reaper without opening a project. If it opens a project, close the project.

Hit CTRL + P to open preferences. (good trick to know anyway, everything you need is there).

Scroll down on the left of Preferences to Plugins / VST.

Make sure you’ve allowed the folder the VST is in, in the VST paths. If not, add it, or close the program and move the unzipped MicrotonalPolyWorms folder into the VST folder.

On the right pane of Preferences / Plugins / VST hit “re-scan.” It will take a second to re-scan.
Then hit Clear Cache / Re-scan. If you have a lot of VSTs, it will take a while. If not, a few seconds.

Now open a project. Add a track. Click the green FX button on a track. Click, Add to bring up the FX list. Look for Microtonal Poly Worms under NEW. If you don’t see a New, look under developers / Michael W. Dean. Should be there. Add it, and use it.

NOTE, IN REAPER, and this is not intuitive, you need to click “Arm for Record” (“Record Arm”) on a track to use a MIDI device. “Arm for Record” is the brown round button on a track. It will turn red when armed. (Then to record, hit the similar larger button at the top of the program.)

Also set your MIDI input for your device, or start with

Input / MIDI / All MIDI Inputs / All Channels.

mail us Contact BipTunia. (Also get a free BipTunia sticker)

11 thoughts on “VST synth, “Microtonal Poly Worms” v2.1 – has 5374 tunings (!), 64 presets. Polyphonic, microtonal, free, easy to use, robust.

    1. No, I don’t know how. And can’t spend money to do it, since I give this away.

      I’d recommend spending 50 bucks on a cheap used Windows computer on eBay. If you want recommendations I can help.

      That would be still a lot cheaper and easier to get into microtonal music production than it was even a couple years ago.

      There are ways to do microtonal music on Mac, but they’re not nearly as easily as running this app on Windows.


  1. Hey, I’m happy to discover your site- love Sevish’s stuff, and am a free VST fan (alright- who said “Hoarder”? I heard that!). Really appreciate all the documentation, and happy to see another microtonal synth- the only ones made purposefully for it that I was aware of before were the Xen-Arts synths. I have to inform you that, while it won’t scare the likes of me away, the GUIs (and SynthEdit origins) of Shiny Dirt and MPW are not likely to draw thousands of converts to the microtonal cause. If I had GUI skills I’d offer to help create alternate versions, but Limeflavour, I’m not. Anyway, off to investigate the rest of that which is BipTunia, cheers!

    1. Thanks.
      The GUIs are intentional. They’re meant to scare off most people.
      Most people are idiots.
      These VSTs are only for cool people who see beyond the surface.

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