FB-3100

Name: FB-3100
Author: Full Bucket Music

by Full Bucket Music · Synth · KORG PS-3100 emulation

Not rated yet

FB-3100 is a free emulation of the KORG PS-3100 from 1977, a fully polyphonic semi-modular synth with a patch panel and resonators section.

It has band-limited oscillators, two-pole lowpass filters, two modulation generators with sample and hold, and micro-tuning; it is free.

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

Keywords: hardware emulation, polyphonic, free, ensemble, 70s, modular, strings, organ, analog-sounding, extreme, inspired by, pads, paraphonic, punchy, resizable UI, skeuomorphic, sound design, tempo-synced, textures.

What it does

FB-3100 is a free simulation of KORG's PS-3100 from 1977, the smallest of the PS series polysynths, with one synth bank and a semi-modular patch panel. The developer aims for "close emulation of behavior and all controls of the original hardware".

Oscillators: one oscillator per voice, 64 voices, with triangle, sawtooth, square, rectangle, pulse and PWM waves at 16' to 2', plus fine and coarse tuning.
Filter: a two-pole lowpass modelled on KORG's K-35 chip, with cutoff, Peak, keyboard tracking and an Expand control for envelope depth.
Resonators: three bandpass filters with individually adjustable centre frequencies and an Intensity mix, modulated by MG2 or the patch panel.
Modulation: MG1 (triangle, rising or falling saw, square, pink and white noise up to 1.6 kHz) and MG2 (triangle), both host-synced, plus sample and hold and ring or cross modulation.
Envelopes: ADSR envelopes with Damp, Half Damp and Release steps and a Hold function, plus a paraphonic General Envelope Generator.
Patch panel: menu-based routing in place of patch cords, with a modulation monitor display.
Ensemble and tweaks: an ensemble effect in the style of 70s string machines, an external audio input before the resonators, Final and Direct outputs with panning, four MIDI CC sources, clock triggers, per-key micro-tuning and MIDI Learn.

The current version is 1.2.2 (1 Jul 2026); the standard builds have a resizable UI. It is a free download, and the developer accepts donations. English and French PDF manuals are available.

Source: Full Bucket Music product page

When to use it

FB-3100 is the simplest way into Full Bucket's KORG PS series: one bank, a patch panel and a mellow filter, all free. Compared with Diva, its filter is softer and less aggressive and the workflow is slower, but the resonators and ensemble give it an organic, string-machine character. Next to CS-80 V, it offers semi-modular patching rather than expressive performance tools. It is smaller in scope than FB-3300, which stacks three such banks.

Best for: polyphonic pads, organ-like tones, ensemble strings, resonant textures and microtonal work.
Genres: ambient, electronic, soundtrack and retro synth music.
Look elsewhere if: you want quick preset browsing (Sylenth1 or Hive 2) or a more beginner-friendly panel; Vital is easier to learn.
Tip: watch the polyphony setting; KVR users note CPU load rises significantly at high voice counts.

What producers say

Reviewers praise its accuracy and efficiency, with only small gripes.

KVR users rate it 5 out of 5 from 1 review; a PS-3100 owner said it "comes extremely close" to the hardware, and others note its punchy sound and suitability for microtonal and organ-like sounds.
Bedroom Producers Blog liked the near-identical front panel, the patch bay ("a joy to use") and the lovely analog-like chorus, and measured under 8% CPU with 10 or more notes.
Criticisms: only 64 factory patches, a panel that may be too advanced for beginners, a subtle crackle when changing oscillator volume with the mouse wheel (BPB, 2017), and higher CPU at high polyphony (KVR).

Where to buy

Full Bucket Music: Free

Tutorials and reviews

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