Kern

Name: Kern
Author: Full Bucket Music

by Full Bucket Music · Synth · Performance synth

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Kern is a free polyphonic performance synth designed for use with MIDI keyboard controllers, with two oscillators with hard sync and a four-pole lowpass filter in two types.

It has two envelopes, an LFO, chorus, 64 voices and 32 factory presets by Alberto Rodriguez; it is free.

Best for: Keys & Synths, Sound Design. Genres: Electronic & EDM, Pop.

Keywords: free, simple, polyphonic, monophonic, basses, CPU-light, FM, leads, pads, punchy, resizable UI, smooth, sound design, thin.

What it does

Kern (German for "core") is a free performance synth from Full Bucket Music, "streamlined to be used with MIDI keyboard controllers". Its parameter count is cut to roughly the number of knobs and sliders on a typical master keyboard, so every parameter can have its own hardware control.

Oscillators: two band-limited oscillators sharing one waveform choice, Sawtooth or Square. Oscillator 2 transposes ±24 semitones and detunes ±1 semitone, and can be hard-synced to oscillator 1.
Pitch modulation: FM depth from the LFO or the filter envelope (positive or negative), plus portamento.
Filter: zero-delay-feedback lowpass in two types: Smooth, a four-pole filter that can self-oscillate, and Dirty, a punchier two-pole filter that does not.
Cutoff modulation: filter envelope amount, LFO amount, key tracking and velocity tracking, all usable together.
Envelopes and LFO: a simplified filter envelope (Attack, Decay/Release, Sustain on/off), an amp envelope with its own Release, and one LFO (Triangle, Square, S/H) from 0 to 100 Hz that also gives mod-wheel vibrato.
Chorus and voices: a chorus with two LFO rates and depth, up to 64 voices, and a mono mode with single or multiple triggering.
Two panels and MIDI: a traditional layout and an alternative panel that mirrors the controls of a hardware keyboard such as the Novation Impulse. Parameters come pre-mapped to CCs (for example CC41 for cutoff, CC42 for resonance) and can be remapped with MIDI Learn.

It ships with 64 factory patches, presets 32 to 62 by Alberto Rodriguez, and supports MTS-ESP micro-tuning and a resizable UI. The current version is 1.2.0 (12 February 2025), and English and French manuals are available. It is a free download; the developer accepts donations.

Source: Full Bucket Music product page

When to use it

Kern is the better pick when you want a free synth you play from a keyboard, with one knob per parameter and almost no CPU load. Compared with Hive 2 and Sylenth1, it covers a much smaller slice of subtractive sound, with one filter, one LFO and no effects beyond chorus, but it needs no menus or mapping to play live. Unlike Vital, it has no wavetables or modulation matrix. Next to Full Bucket's own The blooo, it gives up the second filter, extra waveforms and deeper modulation in exchange for a fixed CC layout that suits hardware controllers.

Best for: live keyboard playing and simple basses, leads and pads at very low CPU cost.
Genres: electronic and pop.
Look elsewhere if: you want many oscillators, effects and modulation; Hive 2 or Vital are more capable, and The blooo goes deeper for free.
Tip: switch the filter to Dirty for grit; Bedroom Producers Blog found it "distorts quite easily and sounds really good".

What producers say

Coverage is thin and mostly from its 2015 launch, but the one hands-on write-up was very positive about the sound.

Bedroom Producers Blog (Tomislav Zlatic, 2015) said Kern "sounds really good. And I mean REALLY good" and liked its MIDI-keyboard-first design.
Trade-off: the same review called it "a simple synthesizer" with a reduced feature set, which it saw as a strength rather than a flaw.

Bedroom Producers Blog article

Where to buy

Full Bucket Music: Free

Tutorials and reviews

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