Full Bucket Music has released FB3, a free software emulation of the 1986 Kawai K3 and K3m hybrid synthesizers for macOS and Windows.
If the name FB3 sounds familiar, that might be because we previewed FB3 in July, when Espen Kraft demonstrated a beta version and the plugin was not yet publicly available. Version 1.0.0 is now finally ready to download from the official Full Bucket Music website.
The finished release also clears up one question from the preview: the K3’s additive User Wave editor did make it into FB3. That is great news because creating a custom waveform from individual harmonics was one of the original instrument’s coolest features.
The K3 was Kawai’s first hybrid synth. It combined an 8-bit digital wave generator with analog filters and amplifiers. Its oscillators ran at a fixed 41.667 kHz sample rate, while the analog section used the same SSM2044 filter chip found in classics such as the Korg Polysix and PPG Wave 2.2.
FB3 follows that general architecture with two digital oscillators per voice, 31 ROM waveforms, white noise, and two User Wave slots. You can build a User Wave from up to 32 harmonics, with 32 intensity levels per harmonic, or import a mono WAV file and let FB3 convert it into the instrument’s internal format.
Unlike the original hardware synth, which made 50 programs share a single internal User Wave, every FB3 program stores its own internal and cartridge waves. Either oscillator can use either wave, making the system much more flexible.
The rest of the engine includes a resonant low-pass filter, a global high-pass filter, separate filter and amp ADSR envelopes, seven LFO shapes, velocity and aftertouch modulation, portamento, and a multi-mode chorus. Polyphony is adjustable from one to 64 voices, while Mono mode stacks six slightly detuned voices.
FB3 includes the original factory sounds and 100 program slots arranged as 50 internal and 50 cartridge programs. It can import and export SysEx patches and User Waves, and its interface can also act as an editor for a real K3 or K3m.
Modern additions include a resizable interface, MIDI Learn for every parameter, host-synced LFO rates, and MTS-ESP dynamic microtuning support.
The download is available directly from the website, with no account, email signup, or checkout required. Windows users can choose VST2/VST3, CLAP, or AAX ZIP packages. The Universal Binary 2 macOS installers cover Intel and Apple Silicon in VST2, VST3, AU, CLAP, and AAX formats.
One installation note for Mac users: you may need to right-click it and select Open, then select Open Anyway in Privacy & Security on newer macOS versions.
Download: Full Bucket Music FB3 (FREE)
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Last Updated on September 7, 2026 by Tomislav Zlatic.
