Penumbra

1. Introduction

Penumbra is a real-time granular processor (VST3) that continuously captures incoming audio into a circular buffer and scatters it back as overlapping grains - tiny windowed slices of the recorded sound. By controlling grain size, density, position, pitch, and spread, you can transform any incoming signal into evolving textures, lush pads, rhythmic stutters, or impossible atmospheres.

The plugin combines a live grain engine with two tempo-syncable LFOs, an envelope follower, a built-in stereo delay and reverb, MIDI triggering, burst mode, an interactive XY pad, and a motion recorder that captures and replays your XY gestures. Everything is designed to run in real time without pre-loading samples - whatever you feed it becomes the material.

Key Features

• Live grain capture (no sample loading) with 0.1–30 second buffer
• Polyphonic grain scheduler with up to dozens of simultaneous overlapping grains
• Four window shapes (Hann, Triangle, Trapezoid, Blackman)
• Pitch shift ±24 semitones with optional musical-scale quantization
• Per-grain filter (low-pass / high-pass) with separate “grain filter” tone
• Freeze + Reverse + Feedback for sustained textures and self-oscillation
• Two LFOs with five shapes and DAW tempo sync, each routed to your choice of destination
• Envelope follower with five routing destinations
• Built-in stereo delay (with ping-pong) and reverb
• MIDI note trigger with velocity sensitivity
• Burst mode (fires 2–8 grains per trigger for stuttered hits)
• Interactive XY pad with motion recording and playback
• Real-time waveform display showing buffer contents and grain positions
• Preset browser, parameter locks for randomization, A/B undo/redo

How Granular Synthesis Works

Penumbra writes incoming audio continuously into a circular buffer of configurable length. A scheduler then triggers short overlapping grains read from anywhere in that buffer. Each grain is shaped by a window function (a smooth envelope that fades it in and out), independently pitched, panned, and filtered, then summed with all the other live grains into the output. By layering many overlapping grains per second - sometimes dense clouds, sometimes sparse fragments - the result ranges from subtle thickening to complete deconstruction of the source.

2. Installation

System Requirements

• Windows 10 or later (64-bit)
• A VST3-compatible DAW (Bitwig, Ableton Live, FL Studio, Reaper, Cubase, Studio One, etc.)
• 4 GB RAM minimum
• Intel / AMD x64 processor (SSE4.2+)

Install Steps

1. Close your DAW.
2. Copy Penumbra.vst3 to your VST3 plugin folder (typically C:\Program Files\Common Files\VST3 or your custom VST3 path).
3. Restart your DAW - it should rescan and detect Penumbra under the Apophenia manufacturer.
4. Insert Penumbra as an effect on an audio track or bus.

3. Quick Start

Five steps to hear Penumbra in action:

1. Insert Penumbra on a track containing audio (a pad, drum loop, vocal, anything sustained works best).
2. Set Dry/Wet to around 60–80% so you hear plenty of the granular signal.
3. Hit play. You should hear granular streams - if not, turn Grain Density up.
4. Sweep Position from left to right - you are scrubbing through the live buffer.
5. Push Pitch Random up to about 6–12 semitones for evolving texture.

4. Interface Overview

Penumbra’s interface is organized into functional sections, each grouping related controls. The top of the window shows the plugin name, version, and global status indicators (Freeze, MIDI, Delay, etc.).

Section Layout

• Header - plugin name, version, preset browser, A/B, undo, randomize, menu.
• Waveform Display - live buffer contents with current grain positions overlaid.
• Grain Engine - size, density, position, position random, stereo spread.
• Pitch - pitch shift, pitch random, scale quantization.
• Tone - filter cutoff, filter type, window shape, grain filter.
• Modulation - LFO 1, LFO 2, envelope follower.
• FX - delay, reverb.
• XY Pad - two-axis controller with motion recording.
• Output - dry/wet, output gain, input gain, stereo width, peak meters.
• Status Bar - hovered-control tooltip and active mod indicators.

Signal Flow

5. Parameter Reference

All controls support right-click for context menu (set default, enter value, lock from randomize). Hover any control to see its current value and a brief description in the status bar.

5.1 Grain Engine

5.2 Buffer & Position

5.3 Pitch & Quantization

5.4 Window & Filter

5.5 Stereo

5.6 Freeze, Reverse, Feedback

5.7 LFO 1 & 2

5.8 Envelope Follower

5.9 Delay

5.10 Reverb

5.11 MIDI Trigger

5.12 Burst Mode

5.13 Mix & Output

6. XY Pad & Motion Recorder

The XY pad gives you simultaneous control over two parameters with mouse or touch. Both axes can be re-assigned via right-click menu on the pad.

Motion Recorder

Below the XY pad, a record button captures your gesture motion. Once recorded, the playback button replays the gesture in a loop, automating the two assigned parameters with whatever timing and shape you played. Useful for hands-free evolving performances or for layering automation that would be tedious to draw.

• Record - arms the recorder. Move the XY pad to capture motion.
• Play - loops the recorded gesture continuously.
• Stop - halts playback and returns to manual control.
• Clear - erases the recorded motion.

7. Presets

Penumbra ships with a curated factory preset bank covering pads, textures, stutters, rhythmic grains, ambient drones, and creative experiments. Use the preset browser (header bar) to step through presets with the < and > arrows or select directly from the dropdown.

User Presets

User presets are saved as XML files in %APPDATA%/Penumbra/Presets/ with the extension .gfxpreset. Click Save in the preset browser, give your preset a name, and it will appear under the User category in the dropdown.

Randomize & Parameter Locks

The RND button randomizes most parameters within musically useful ranges. To prevent specific parameters from being randomized, hold Ctrl and click any knob to lock/unlock it - locked knobs are marked visually and skipped during randomization.

8. Tips & Tricks

A. Appendix: Full Parameter Reference

Grain Engine

Pitch

Filter & Tone

Sustain

LFOs

Envelope Follower

Delay

Reverb

MIDI & Burst

Mix & Output