Tine · E-Grand · Reed · Grand · Clav — VST3 · AU · CLAP · Standalone
Epi computes every note from the physics of the instrument: a hammer strikes a piece of steel, the steel rings, and a transducer — or, on the acoustic grand, a pair of microphones — turns its motion into a signal. There is no sample library and no oscillator standing in for one — when you change the hammer, the pickup, or the steel itself, the sound changes the way it would on the real bench.
Five instruments live behind one selector:
- Tine — the classic tine piano: 88 tuned steel rods with tone bars, magnetic pickups, and the stereo panner its amplifier called vibrato. The harmonics come from the pickup's field, not the metal — which is why the pickup HEIGHT knob re-voices the instrument the way the real voicing screw does, and why playing harder growls instead of just getting louder.
- E-Grand — the electric stage grand: real strings on a rigid bridge with a piezo pickup that reads string force, a mid-scooped preamp, and the long singing sustain that made these tour.
- Reed — the reed piano: solder-tuned steel tongues over an electrostatic pickup polarised at 150 volts. The louder you play, the more the gap's asymmetry barks — that snarl is the geometry of the pickup, and the SUPPLY knob is a real voltage.
- Grand — an acoustic grand: 88 notes of one to three strings each on a fitted soundboard, radiated through a spaced mic pair. Decay knees, the bass-left stereo image, half-pedal and the pedal-open board wash all come out of the same coupled model, verified row by row against measurements of a real instrument.
- Clav — a tangent-action string keyboard: sixty strings struck and held against an anvil, twin bar pickups at their measured distances with a 4-way selector (center, bridge, both, out of phase), four tone rockers computed as the real RC networks behind them, and the measured three-semitone pitch drop when the tangent lets go and the yarn-wrapped dead length rejoins the string.
Every voice is its own mechanism. All 88 notes have their own hammer, their own resonator, their own pickup — chords never steal voices and repeated notes meet steel that is already moving. Sympathetic resonance runs on every model, with the partial-coincidence hierarchy of a real harp: on the string piano a struck note rings its octave partner 19 dB down, the twelfth 26 dB down, and the non-coincident wash 38 dB down.
Every resonator has a MATERIAL selector: music wire, stainless, bronze, brass, titanium, aluminium, tungsten, nylon. These are real material constants, not tone presets. The geometry re-solves at the same pitch, so inharmonicity scales as stiffness over density — bronze halves the partial stretch, and titanium lands on steel's curve because its ratio genuinely matches. Internal loss enters per mode, and on strings only through the bending share — which is why a nylon string sustains while a nylon rod clunks. A bare conductor reaches a magnetic pickup only as the faint eddy signal its conductivity allows: aluminium sits 17 dB under steel, titanium is a whisper, and nylon — an insulator — is silent, exactly where it must be.
The transducer is swappable too: magnetic, the instrument's native transducer, electrostatic, or contact, on any resonator, with a position control wherever the geometry supports one. The factory presets are tested against the pairing rules, so no shipped sound is a silent material-transducer combination.
- Sustain (CC64) is read as a continuous value, not a switch: the damper felt compresses the way a real damper rail does, so half-pedalling works, with the felt-compression curve included.
- Sostenuto (CC66) latches exactly the keys held at the moment the pedal falls (the grand — the electrics never had a middle pedal).
- Una corda (CC67) shifts the grand's action so the hammer meets two strings of a trichord and one of a bichord, and monochords meet fresh, softer felt.
The panel gets you the classic sounds. The workshops let you rebuild the instrument.
- Tine / String workshop — re-cut any note's steel. The LENGTH lane retunes by the beam and string equations (paint microtonal scales by hand, or apply just intonation, Pythagorean, quarter-comma meantone, Werckmeister III, slendro, pelog, an octave stretch, or a barroom scatter with one click, rotated to any root). The GAUGE lane swaps the wire: pitch stands, and the overtone character moves — fat wire turns the tine bank into gongs and the grand's strings bell-like.
- Pickup workshop — every pickup gets its own height, gap, and winding. Three tolerance templates paint the manufacturing scatter of a well-kept, worn, or neglected instrument — deterministic, so your instrument is the same one every session.
- Cabinet workshop — a speaker with dimensions instead of an impulse response: box volume sets the resonance, cone size sets the breakup, the microphone has distance and angle, and the suspension decides when it grinds. Five cabinets ship as one-click starting points.
- Mic Studio — the grand's bench, in two modes. Classic Pair: spread widens the calibrated pair and deepens the bass-left image, balance walks it, distance is the lid's high-band shadow, each mic has its own trim. Stage: up to five microphones dragged freely on a top-down view of the instrument, each rendered from real geometry — inverse-distance level (6 dB per doubling, measured), arrival delay at the speed of sound, the board's dipole (a mic under the board reads the low band inverted), and the lid as a specular image that brightens the open side. The whole five-mic stage costs about 2% of a core.
Everything the workshops hold is saved in your project and inside every preset you save — a saved sound is the whole sound. Factory presets ship across all five instruments, and every one of them is rendered and measured by its own test harness (levels, character claims, legal material-transducer pairings) before it ships.
- Click the drawn keys (deeper on the key is louder) or play A–; on your computer keyboard — or just send it MIDI, including the three pedals (CC64/66/67), expression (CC11), and pitch bend.
- The visualizer is telemetry, not animation: every rod swings at its true frequency by the measured amount, hammers fire when the engine strikes, and a SUSTAIN lamp shows the pedal state your keyboard is actually sending.
- BASS, TREBLE, and CLARITY are the channel strip; DRIVE and CORE SAT (or SUPPLY, on the reed piano) are where the dirt lives, because that is where it lives on the instruments.
- ROOM and SIZE place the output in a space, and SPACE picks which one: the adjustable studio room the plugin shipped with, or one of five surveyed profiles — booth, studio, stage, hall, church — each with its decay computed per octave band from published absorption data and its early reflections from the room's actual geometry. The size knob scales the surveyed room's dimensions and the physics follows.
- The five instruments are level-matched to within a decibel at a shared -18 dBFS mezzo-forte bench — except the grand, deliberately about 6 dB under, because its real 22 dB attack crest must clear the output rail (transparent below 0.76, bounded a decibel under full scale). Switching instruments fades through silence, and fast knob sweeps glide instead of clicking.
Grab the zip for your platform from Releases, unzip, and copy the plugin bundles to your plugin folder (an INSTALL.txt with the exact paths is inside each zip).
macOS builds are unsigned: right-click → Open the standalone once, or run
xattr -cr on the bundles, and your DAW will load them.
Formats by platform, exactly as CI ships them:
| VST3 | AU | CLAP | Standalone | |
|---|---|---|---|---|
| macOS (universal) | yes | yes | yes | yes |
| Windows (x64) | yes | – | yes | yes |
| Linux (x64) | yes | – | yes | yes |
Building from source needs CMake ≥ 3.22 and a C++20 compiler; JUCE is a
submodule. cmake -S . -B build && cmake --build build --target Epi_All.
Measured, not asserted. The models are calibrated against recordings of the
real instruments and against the published measurements of the people who
put them under high-speed cameras and spectrum analysers — and the repo
carries the receipts: eight test suites of numbered rows render audio
offline and measure it, from inharmonicity curves and per-partial decay
rates to "a chord must equal the sum of its notes on the piezo bridge, and
must NOT on a coupled soundboard". One suite per model family (tine, reed,
grand, clav), one for the DSP cores, one that renders every factory preset
and holds it to its own claims, one for the engine's seams (instrument
switching, pedals, knob-sweep clicks, the output rail), and one that
round-trips plugin state through the real processor — all run in CI on
macOS, Windows, and Linux. docs/ holds the implementation plans and the research notes
with every number's provenance.
Fender, Rhodes, Wurlitzer, Yamaha, and Hohner are trademarks of their respective owners. Epi is not affiliated with, endorsed by, or sponsored by any of them; their names appear only in the documentation, factually, to identify which instruments were measured.
GPL-3.0. The DSP is plain C++ headers with the physics explained in the comments — if you want to know why a knob does what it does, the answer is in the file, usually with the measurement that decided it.