Membrum

Features

• 32-pad grid (4×8) — MIDI notes 36–67 mapped to a 4-row, 8-column pad layout with per-pad glow reflecting voice activity, level, and category color coding
• 6 exciter types — Impulse, Mallet, Noise Burst, Friction, FM Impulse, and Feedback (with energy limiter). Velocity-controlled spectral response: soft hits dark, hard hits bright
• 6 body models — Membrane (48-mode Bessel), Plate (48 modes), Shell (32 modes), String (waveguide), Bell (16 Chladni modes), and Noise Body (40 modes + broadband layer)
• Per-mode damping law — Chaigne-Askenfelt (1993) `R_k = b1 + b3·f²` so the same body can dial from metallic ring (low b3) to woody thump (high b3) without touching the fundamental
• Air-loading correction — Rossing-tabulated low-mode frequency depression for realistic kick / tom sub-bass; per-pad blend between pure Bessel and full Rossing curve
• Head ↔ shell coupling — Optional second modal bank (24 shell modes) running in parallel with bidirectional energy exchange. Stability-clamped two-bank feedback loop; closes the “no body weight” gap on kicks and toms
• Nonlinear tension modulation — Energy-dependent pitch glide reproducing the 808 / acoustic-tom “kerthump”: 20 ms energy follower drives block-rate frequency scale, depth scaled by velocity²
• Parallel noise + click layers — Always-on filtered noise alongside the modal body plus a 2–5 ms raised-cosine attack click. Per-pad mix, cutoff, resonance, color, decay, and contact time
• Tone Shaper — Per-pad signal-shaping chain: drive (alias-safe waveshaper) → wavefolder → DC blocker → SVF filter (LP/HP/BP) with dedicated 4-stage filter envelope, plus absolute-Hz pitch envelope (start, end, time, exp/lin curve) for 808-style transient sweeps
• Unnatural Zone — Mode Stretch (0.5–2.0), Decay Skew (±1), Mode Inject with phase randomisation, Nonlinear Coupling with energy limiter, and Material Morph (2-point envelope, 10–2000 ms)
• 5 per-pad macros — Tightness, Brightness, Body Size, Punch, and Complexity. Each maps to a curated set of underlying parameters via incremental delta application; underlying parameters remain independently automatable
• Per-pad enabled toggle — Click the bottom-right power glyph on any pad to silence it without touching its parameters; disabled pads silently short-circuit at note-on (no allocator, no choke)
• Acoustic / Extended UI mode — Session-scoped toggle that filters the selected-pad panel to natural-drum essentials or the full extended parameter set. All parameters remain reachable via host automation regardless of mode
• Up to 16-voice polyphony — Configurable max polyphony (4–16) with three voice-stealing policies: Oldest (allocator-driven), Quietest (amplitude scan), and Priority (highest-pitch stolen first, protects kick/snare). 5 ms exponential fast-release prevents click on steal/choke (peak click ≤ -30 dBFS)
• 8 choke groups — SoundFont 2.04 Exclusive Class semantics: hi-hats and other choke-paired pads cut each other on note-on with cross-group isolation
• Multi-output routing — 16 stereo output buses; per-pad bus assignment lets you route ride / cymbals / drones to dedicated buses for separate DAW processing
• Coupling system — Global Coupling, Snare Buzz, Tom Resonance, and Coupling Delay knobs plus per-pad coupling amounts produce sympathetic resonance between pads (toms ring the snare wires, kick excites the floor tom, etc.)
• Master output gain — [-24..+12] dB range with 6 dB of default headroom; main bus only (aux buses pre-master)
• Custom VSTGUI editor — 4×8 pad grid, selected-pad parameter panel with fieldset organisation, kit and per-pad preset browsers, voice-management UI, output-routing UI, coupling section with formatted value displays. Cross-platform via VSTGUI only
• 20 factory kit presets — 5 each across Acoustic (Studio Kit, Jazz Brushes, Rock Big Room, Vintage Wood, Orchestral), Electronic (808, 909, LinnDrum CR-78, Modular West Coast, Trap Modern), Percussive (Hand Drums, Latin Perc, Tabla, World Metal, Cajon & Frames), and Unnatural (Experimental FX, Glass Bell Garden, Drone & Sustain, Chaos Engine, Ghost Bones)
• Real-time safe — Zero allocations on the audio thread; all DSP banks pre-allocated. ExciterBank and BodyBank pre-allocate every variant up front; voice switches via tagged-union dispatch with no virtual calls or per-sample branching
• Cross-platform — VST3 (Windows, macOS, Linux) + Audio Unit (macOS), pluginval strictness 5 verified on Windows, auval verified on macOS

Exciters

Each pad picks one of six excitation models. All exciters scale spectral content with velocity so the same pad sounds darker when struck softly and brighter when struck hard.

• Impulse — Single-sample velocity-scaled impulse for sharp, clean attacks. The reference exciter for kicks and rim shots
• Mallet — Raised-cosine contact pulse with velocity-controlled contact time. Longer attack with more body tone; the canonical tom and timpani exciter
• Noise Burst — Filtered-noise excitation with controllable burst duration. The basis for snares, hi-hats, cymbals, and brushes
• Friction — Bowed / scraped excitation with controllable pressure for sustained drones, singing bowls, and brush sweeps
• FM Impulse — Two-operator FM impulse with selectable carrier-modulator ratio for metallic, bell-like, and digital-cowbell tones
• Feedback — Self-exciting feedback loop with built-in energy limiter for chaotic, runaway-resonance percussion

Body Models

The body model determines how the exciter's energy maps to a pitched, resonant tail. Each model is a parallel modal resonator bank with research-backed mode ratios.

• Membrane — 48 Bessel-function modes for circular drum heads. Air-loading correction depresses the lowest modes for realistic kick and tom sub-bass. The reference body for kicks, snares, toms, and hand drums
• Plate — 48 plate-mode ratios for rim shots, claves, cajón fronts, and side sticks. Higher modal density than membrane gives a denser, more inharmonic spectrum
• Shell — 32 cylindrical-shell modes. Often used as the secondary bank in head/shell coupling, but stand-alone for woody side sticks and cajóns
• String — Waveguide string body with mode-stretch control for tubular bells, mbiras, bowed drones, and tabla tanpura
• Bell — 16 Chladni-pattern bell modes with metallic damping (b3 = 0). FM-driven bells produce cowbells, agogos, crotales, and singing bowls
• Noise Body — 40-mode hybrid plus a broadband noise layer. The cymbal body: high inharmonic mode density for crashes, rides, and hi-hats with shimmer-tail noise mixed back into the modal sum

Factory Kits

20 factory kits ship with the plugin, organised into four browser subcategories. Kits author their own UI mode (Acoustic or Extended) and ship per-pad macro defaults so the Tightness / Brightness / Body Size / Punch / Complexity knobs sweep meaningful sound design ranges out of the box.

• Acoustic (5) — Acoustic Studio Kit, Jazz Brushes, Rock Big Room, Vintage Wood, Orchestral
• Electronic (5) — 808 Electronic Kit, 909 Drum Machine, LinnDrum CR-78, Modular West Coast, Trap Modern
• Percussive (5) — Hand Drums, Latin Perc, Tabla, World Metal, Cajon & Frames
• Unnatural (5) — Experimental FX, Glass Bell Garden, Drone & Sustain, Chaos Engine, Ghost Bones

Per-pad presets are saved separately and can be loaded onto any pad without disturbing the rest of the kit's routing, choke groups, or coupling state.