KVR Developer Challenge 2021 – Download 37 FREE Audio Plugins


KVR Developer Challenge 2021 is now officially live and 37 brand new free VST plugins are available for download.

For those unfamiliar, KVR Developer Challenge is a plugin development contest hosted by KVR Audio. It’s launched every few years and everyone can enter by submitting a plugin or a sound library.

See also: 99 Drum Samples II Is A FREE Drum Sample Pack By 99Sounds

The best thing about the contest is that all submissions are available for free download.

Knowing that the previous iterations of the contest brought us classic freeware plugins like Youlean Loudness Meter, Lagrange, and Triple Cheese, it’s hard not to be excited about this year’s entries.

Here’s an overview of some of my favorite entries in the KVR Developer Challenge 2021.

WhispAir by Full Bucket Music

WhispAir by Full Bucket Music

WhispAir by Full Bucket Music

WhispAir is a virtual wavetable synthesizer with three DCOs and an additional noise generator, four al envelopes, a trio of LFOs, a multi-mode filter, and a stereo chorus effect.

Coming from Full Bucket Music, the developer behind some of the best free synths on the market, WhispAir is a virtual instrument worth your attention.

It seems to take inspiration from the hardware hybrid synths of the late 80s, such as the Korg DW-6000 and Ensoniq ESQ-1. These instruments combined digital oscillators with analog filters, resulting in more polyphony and some unusually complex timbres.

As expected from a Full Bucket Music product, WhispAir is well-designed, with a complex but easy-to-use interface. It delivers that authentic hybrid synthesizer tone while retaining a low CPU hit.

Reducktion by Dead Duck Software

Reducktion by Dead Duck Software

Reducktion by Dead Duck Software

Reducktion is a polyphonic virtual synthesizer by Dead Duck Software. Its name is a throwback to Deducktion, the developer’s KVR DC 2018 entry.

The instrument offers 32 voices of polyphony while featuring three multi-mode oscillators, two filters, an eight-voice stereo unison, three envelopes, three LFOs, an arpeggiator, and a flexible modulation matrix with twelve modulation slots.

Whereas Deducktion focused on subtractive synthesis, Reducktion takes things a few notches further with its FM oscillator, a continuously variable Wave oscillator, and the unison effect.

The 16-step oscillator is another highlight, offering multiple playback modes, modulation, and a variable step count.

GR-8 by Phuturetone

GR-8 by Phuturetone

GR-8 by Phuturetone

GR-8 is a virtual analog synthesizer developed by Phuturetone. It seems to be the same developer who released Phutura, a freeware Alpha Juno emulation from 2011.

The instrument features a somewhat basic dual-oscillator synthesis engine. However, its sonic arsenal is all but basic, thanks to the oscillator effects (FM, PWM, sync), four available voice modes (Mono, Unison, Chord, Poly), a robust arpeggiator module, and a selection of built-in effects (EQ, Phaser, Chorus, Distortion, Reverb, Delay).

GR-8 comes with a well-designed interface, modulation controls, and 88 presets to help new users get started. 




STFU is a simple but effective faux-sidechain effect by ZEEK. It syncs to the host’s BPM setting automatically, and it’s triggered via MIDI.

The user can fine-tune the volume envelope’s timing and cross-fade between two envelopes to create more complex effects.

The plugin features a helpful real-time waveform display which acts as the background for the envelope editor.

Transperc by Apisonic Labs

Transperc by Apisonic Labs

Transperc by Apisonic Labs

Transperc is a free transient shaper by Apisonic Labs. Use it to amplify the attack transient or to add more sustain to percussive sounds.

The plugin also features a built-in filter (high-pass and low-pass), a mix knob, and a clipper module which is handy for catching any excess volume peaks.

FKFX Influx by FKFX

FKFX Influx by FKFX

FKFX Influx by FKFX

FKFX Influx is an interesting audio effect by FKFX, the same developer who recently released FKFX the Obvious Filter plugin.

It’s hard to categorize FKFX Influx since it is such an unusual plugin. Instead of simply labeling it as a multi-effect, let’s mention its most exciting features.

The plugin transforms the incoming signal with a resonator and a tube distortion unit. It features a multi-point LFO editor in the resonator module, 38 scale modes, a filter, waveshaping, and more.

FKFX Influx comes with 82 included presets, which is more than enough to get started. If you want more presets, download 128 additional patches for free from the Heat Audio page on Facebook.

KVR Developer Challenge 2021

Visit the contest page linked below to check out all 37 entries. All plugins are available for direct free download, so you don’t need to sign up or provide your email address.

That said, KVR Audio’s online community is one of the best around and it’s the place where I learned so much about audio plugins and music production software. So, consider checking out their forum for some friendly music software banter.

More info: KVR Developer Challenge 2021

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About Author

Tomislav is a music producer and sound designer from Belgrade, Serbia. He is also the founder and editor-in-chief at Bedroom Producers Blog.


  1. I already have so many plugins I rarely use, but now it’s time to get more and perhaps even find some I’ll use more than once! Didn’t know this was a thing. Thanks for the info, Tomislav.

  2. Great Menu :)

    trying to install GR-8 by Phuturetone but don’t find the vst, no dir option during the install…where is it located ? (windows7)

    • It gets installed into the VST3 folder which is usually found in Windows 10 in: Program Files/Common Files/VST3. Just add that folder to the folders your DAW scans for VSTs, and it will show up in your DAW.

        • Thanks it worked
          A lot of bugs yet … some presets doesn’t work and midi learn datas are not stored, when you change your presets all midi learn are deleted :( didn’t find a way to contact Phuturetone to let them know

          • It looks great, but it spikes the CPU rather horribly, can’t really use it as it is now. My system is Windows 10 64 bit FL Studio 20, 16GB RAM, i5 computer

  3. Some great names returning, some healthy newcomers… TBH I only had time to play a bit of WhispAir last night and it’s great for those 80s PPG and DW-esque in a very clear and easy to use package. Full Bucket has a second entry in the form of a granular effect, I’ll be sure to try this one tonight. Reducktion looks interesting, Dead Duck has quite a decent line-up of tools. Great to see Phuturetone, I still like that Alpha Juno they did, unfortunately it never was remade as 64bit, but as a Reaktor instrument. Seems GR-8 doesn’t have those sweet sweet OSC shapes though, why? Anywho, some interesting looking stuff there, some open source projects, etc… This weekend is sure gonna be too short.

  4. I tested the CV out in STFU and it works really well. You can even use it for sequencing pitch cv to modular synths or VSTs like Voltage Modular that have an audio input.

  5. 💥💥💥💥💥 FKFX Influx is an instant “Sonic Retox” engine. The resonator module (FLUX) goes thru a Low Pass and a Tube distortion. Flux resonator Note and Dry/Wet have their dedicated editors.

    FKFX Influx lets you create new grooves from your current input. Selecting “WET ONLY” will output only the transformed part of the signal.

    FKFX Influx comes with 82 Factory preset, plus 128 Extra preset you can get for free directly from Heat Audio facebook (link in preset list), so 210 presets.

  6. A lot of interesting stuff this year! I highly recommend giving Emergence by Daniel Gergely a try, it’s a unique granular delay effect that sounds great and It’s my favorite so far.

  7. Bastiaan de Jong


    STFU is great! Outputting the envelope as cv is really promising. I wish for years there would be a plugin like this. Actually I wish for one with multiple shapes which you could switch easily ;) Anyways… I spent some time to set this up in Reaper. Anyone who’s interested can read this. Not going into too much details:

    1. Create a track with a synth and let it play some tune.
    2. Add STFU on the same track before the synth. Create the shape you wish and set it on CV.
    3. You probably here some ticks because it’s actually a very slow oscilator, like an lfo. Add two outputs on STFU and route the audio to this output.
    4. In the synth turn the knob you would like to automate and open ‘parameter automation/Midi link’
    5. Enable Audio control signal (sidechain)
    6. Select Track audio channel 3+4. Now you should see something happening.
    6. Set attack and release to 0. You could use this to smooth the signal. Which can be useful to remove clicks or if you make trancegate shape with STFU.
    7. Play with the Min volume bar.

    I’m curious if I’m setting up things way more difficult then needed, let me know ;)

  8. My Votes
    5 Points: FKFX Influx
    4 Points: GR-8
    3 Points: Grain Strain
    2 Points: Emergence
    1 Points: WhispAir

  9. gil monteiro


    Most of the presets of GR-8 by Phuturetone don’t work. Am I the only one? I am using it on Reaper.

    • There’s a problem with the Distortion mode called “Satur” in the effects section. Until a possible fix, you can turn it off, you just won’t get the desired effect but still some useable sound. I hope they’ll fix this.

        • I cant even load the GR-8 synth plugin in Cakewalk, everytime there is a vst scan my antivirus starts quarantining these files from the plugin folder of GR-8 (files with a .sem extension) and they don’t seem to exist in the plugin folder even before before the scan, there is only a .vst3 and a .dat and .exe file (for uninstalling the plugin) in there, nothing else….so how is the antivirus removing files that don’t even seem to exist in the first place???

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