Documentation/Orra Filter

Orra Filter User Manual

Version 1.0.0 • © 2026 Orra Audio LLC

Welcome

Orra Filter is a dual-cell filter with a modulation matrix. Each cell can be one of eight filter circuits: a Moog-style ladder, a state-variable filter, a comb, a formant filter, a diode ladder, an MS-20-style Sallen-Key, a resonator bank, and a Spectral filter whose response is drawn by hand. A routing selector places the two cells in series, in parallel, on mid and side, on left and right, or morphs between them.

The modulation sources are four LFOs, an envelope follower, a 16-step sequencer, an ADSR envelope, MIDI velocity, the tracked pitch of the input, four macros, and up to four Orra Link tracks from elsewhere in the project. Any of them can be routed to a cutoff, resonance, drive, FM amount, morph or dry/wet, and to some of the other sources. A route can be made from the MOD MATRIX tab, by dragging a source tab onto a knob, or from a knob's right-click menu.

The response screen shows each cell's frequency response and the combined result, phase included, over the input and output spectra. Optional 2x or 4x oversampling runs the filter block at a higher sample rate; the added latency is a fixed number of samples and is reported to the host.

Also included: DICE, which builds a patch from one of six recipes; a preset browser with categories, favourites and notes; four A/B/C/D snapshot banks; undo; and tooltips in seven languages.

System Requirements

Formats

macOS: VST3, Audio Unit (AU), AAX (Pro Tools). Windows: VST3, AAX.

macOS

10.13 or later. Universal 2, Apple Silicon and Intel.

Windows

Windows 10 or later, 64-bit.

Channels

Mono or stereo. A mono track into a stereo output is duplicated first. An optional stereo sidechain input feeds the envelope follower.

Latency

None with oversampling off. 2x (the default) adds exactly 49 samples, 4x adds 91. The Spectral circuit adds about 17 ms, and a Link A to D pick adds one host buffer. All of it is reported to the host for compensation.

Licence

14-day demo, then activation with your licence key (click the ORRA FILTER wordmark). Activation is shared by every open instance within two seconds.

Interface Tour

The window is organised top-down into five regions on a brushed-bronze faceplate: a header, the response screen, a tab strip, the control band, and a footer. Knobs and keycaps are raised out of the plate; the screen and the selectors are recessed into it.

1. Header

On the left, the ORRA FILTER wordmark, click it any time for the licence and info panel, then BYP (bypass), the four A/B/C/D snapshot banks and RESET. In the centre, the preset strip: the arrows step through every preset, and clicking the name opens the Preset Browser. An edited preset is marked with a dot until you save. To the right: LINK (Orra Link picks), DICE (roll a patch; right-click for recipes), UNDO and REDO, the UI scale selector (75 to 200 percent) and the circular tips toggle. Right-click the tips toggle to choose the tooltip language.

2. Response Screen

The recessed screen draws the live input spectrum in cream, the output in gold, each filter’s own curve in its circuit colour, and the combined response as a white line. Every curve follows modulation in real time. Grab a filter’s handle and drag: horizontal sets cutoff, vertical sets resonance. Shaded bands show how far each cutoff is being swept by its modulation.

3. Tab Strip

Nine tabs choose what the control band shows: FILTERS, MOD MATRIX, LFO 1 to 4, ENV FOLLOWER, SEQ and ADSR. The source tabs are also drag handles: drag LFO 2 onto a knob and LFO 2 modulates it. A tab lights when its source is in use.

4. Control Band

On the FILTERS tab, three cards: FILTER 1, the ROUTING card in the middle (routing selector, MORPH, DRY/WET, STEREO, and the ANALOG / 2X / OSC keycaps), and FILTER 2. Each filter card has the circuit and type selectors, the slope, CUTOFF, RESONANCE, DRIVE, PORTAMENTO, and the ON, MIDI, AUDIO, FM and SHAPE keycaps. On every other tab the band shows that source’s panel, with DRY/WET and MORPH kept in a column at the right so they stay within reach.

5. Footer

IN and OUT gain at the ends, the four MACRO knobs between them. Double-click a macro’s label to rename it; drag the label onto any knob to route the macro there.

Every knob: double-click to return it to default, double-click its value to type a number, Shift-drag for fine adjustment, right-click to add or edit modulation.

How It Works

Two ideas carry the whole plugin.

Two cells, one routing

Filter 1 and Filter 2 are independent cells. Each has its own circuit, type, slope, cutoff, resonance and drive, and each can be switched off without leaving the routing. The ROUTING selector decides how they meet. Off uses Filter 1 alone. Series runs 1 into 2, so a low-pass into a high-pass is a band-pass with two independent edges. Parallel sums them. Mid-Side puts Filter 1 on the mid and Filter 2 on the sides. Stereo Split puts them on left and right. Morph crossfades between their outputs under the MORPH knob. Switching a cell's circuit crossfades over a few milliseconds, so you can audition circuits on a held sound without a click.

Everything is a destination

Every cutoff, resonance, drive and FM amount, plus MORPH, DRY/WET and the output gain, is a modulation destination. A route is a source, a destination, a bipolar depth and a curve. The destination is offset around wherever its knob sits, so the knob remains the centre of the motion. Cutoff depths read in octaves: +1.0 oct sweeps one octave up from the knob at the source's peak.

Routes can also target other sources, so an LFO's rate or depth, or the follower's attack and release, can themselves be modulated. An LFO can breathe another LFO.

Signal flow

input → IN gain → Filter 1 and Filter 2 wired by ROUTING (each cell: drive → circuit, with optional audio-rate FM of the cutoff) → MORPH (Morph routing only) → DRY/WET against the input → OUT gain. With 2X or 4X on, the whole filter block runs at the higher rate behind linear-phase filters. Modulation is computed every 32 samples, so the cells follow fast envelopes and sequencer steps inside a host buffer.

The Controls

All knobs are automatable; every automation lane reads in real units (Hz, dB, ms, %).

Filter 1 & Filter 2

Circuit (eight topologies), The filter’s underlying circuit model. Switching crossfades.

Type (depends on circuit), Moog and Diode: LP, HP, BP. SVF adds Notch, Peak and Allpass. MS-20: LP, HP. Comb: positive, negative, allpass. Formant: one vowel morph. Resonator: the partial set.

Slope (12 / 24 / 36 / 48 dB), Steeper slopes ring more on resonance. 24 dB is the classic Moog voice; 12 dB is gentler.

Cutoff (20 Hz to 20 kHz), Centre or corner frequency, logarithmic. Draggable on the screen. The hero knob.

Resonance (0 to 100 %), Emphasis at the cutoff. Near full the ladders approach self-oscillation; on the SVF it sets Q, on the Comb feedback, on the Formant it narrows the vowel.

Drive (0 to 100 %), Saturation at the filter’s input: up to +24 dB into a tanh shaper with half of it made up again, so it gets louder and dirtier. Level-dependent, so hot sources bite sooner. Use 2X on the ladders.

Portamento (0 to 2000 ms), Glide between tracked notes, constant in semitones per second. Only with tracking on.

ON (on / off), Enables the cell without removing it from the routing, so you can A/B one filter inside a chain.

MIDI / AUDIO (key tracking), MIDI: the cutoff follows incoming notes. AUDIO: it follows the pitch of the audio itself, so on a printed bass or a vocal the filter rides the melody with no MIDI in the project (monophonic sources). Routes still sweep around the tracked pitch.

FM (opens the FM panel), Audio-rate modulation of the cutoff from an internal oscillator or from the input.

SHAPE (Spectral only), Opens the drawn response of the Spectral circuit.

Routing

Routing (Off / Series / Parallel / Mid-Side / Stereo Split / Morph), How the cells combine. Mid-Side and Stereo Split need a stereo track; on a mono track they fall back to series.

Morph (0 to 100 %), Crossfade between the cells’ outputs. 0 is Filter 1 only, 100 is Filter 2 only. Effective in the Morph routing, and a favourite modulation destination.

Dry/Wet (0 to 100 %), Parallel blend of the input against the filtered output. Phase-true even with oversampling on, so a 50/50 blend does not comb-filter.

Stereo (−100 to +100 %), Pulls the left and right cutoffs apart by up to an octave and reads every LFO up to a quarter cycle ahead on the right, so sweeps swirl across the image. Negative flips which side leads. No effect in Mid-Side or Stereo Split.

ANALOG (on / off), Hardware feel: each channel’s cutoff drifts slowly and independently by a few cents, and a faint noise floor keeps resonant settings breathing. Subtle by design; off is bit-exact.

2X / 4X (Off / 2x / 4x), Runs the whole filter block at two or four times the sample rate behind linear-phase filters: cleaner high resonance and hot drive at 44.1 and 48 kHz, at roughly 2x or 4x the filter CPU. Adds exactly 49 or 91 samples of latency, reported to the host. A global setting saved with the session, not changed by presets; the default is 2x. In Ableton Live, switch it with the transport stopped.

OSC (on / off), Lets the ladders self-oscillate. Past about 95 percent resonance the Moog, Diode and MS-20 sing on their own at the cutoff, a clean sine bounded by their loop limiters, and the SVF’s Q ceiling rises. Off, maximum resonance is a long ring that always dies out. Saved with the preset.

Footer

In (−24 to +24 dB), Pre-filter gain. Drive the cells harder without changing the source level.

Macro 1 to 4 (0 to 100 %), Performance macros. Drag a label onto a knob to route it, map a MIDI controller for one-knob control of several destinations, double-click the label to rename. DICE always routes Macro 1.

Out (−24 to +24 dB), Final gain after the dry/wet mix. Match levels with BYP for a fair comparison.

The Eight Circuits

The circuit selector chooses one of eight models per cell. They are separate designs with their own behaviour under resonance, drive and key tracking. Each draws its own curve on the screen in its own colour, phase included, alongside the white combined line.

Moog

The classic four-stage transistor ladder: warm, resonant, takes drive well. Low, high and band-pass ladders at 12 to 48 dB, unity passband at every slope, and the HP and BP ladders resonate right at the cutoff. With OSC on it sings from about 95 percent resonance.

SVF

A clean state-variable filter with little colour of its own. Low, high, band, notch, peak and allpass, with resonance setting the Q. Zero resonance is a Butterworth response, 3 dB down at the knob. Anti-aliased drive. Suited to utility jobs and precise sweeps.

Comb

A short delay with feedback: metallic, robotic, tuned by the cutoff. Positive, negative and a damped allpass. Key-track it and it retunes like a played string; a slow LFO on the cutoff is a flanger.

Formant

Morphs the vowels A, E, I, O, U, with the cutoff as the vowel position. Resonance narrows the formants. Sweep it slowly for talking pads, or route Macro 1 to it and talk by hand.

Diode

A 303-style diode-coupled ladder: softer slope than the Moog, squelchy, the bass thinning as resonance rises. Squelch at 60 to 80 percent; with OSC on it screams at 100.

MS-20

A Sallen-Key with a clipping feedback loop: aggressive, with a screaming resonance and a characteristic bite as it is driven. Low and high-pass.

Resonator

Four tuned peaks at ratios of the cutoff: Harmonic, Odd, Bell, Fifths, Octaves or Unison. Key-track it and it plays like a body. Drums ring like metal, a voice becomes a choir.

Spectral

Draw the response yourself with the SHAPE key: any curve, swept by the cutoff and peaked by resonance. Linear-phase, about 17 ms of reported latency.

Modulation

Three ways to make a route, all ending in the same eight-slot matrix.

  • Drag and drop. Drag an LFO, ENV FOLLOWER, SEQ or ADSR tab, or a MACRO label, onto any knob or onto a cutoff handle on the screen. A callout opens on the knob with the depth and curve.
  • Right-click a knob. The quick-assign menu lists every source; existing routes to that knob show a live depth slider you can drag without the menu closing.
  • The MOD MATRIX tab. Eight rows of source, destination, depth, curve and an on/off. CLEAR removes every route, and it is undoable.

Source, LFO 1 to 4, Env Follower, Seq, ADSR, MIDI Velocity, the tracked input Pitch, Macro 1 to 4, or Link A to D (the level of an Orra Link sender picked in the header’s LINK menu).

Destination, Filter 1 and 2 cutoff, resonance, drive and FM amount; Morph; Output gain; Dry/Wet; and the mod-of-mod targets, which are LFO 1 to 4 rate (free-running LFOs only) and depth, and the envelope follower’s and ADSR’s attack and release.

Depth, Bipolar. Cutoff routes read in octaves, where 100 percent is the whole 20 Hz to 20 kHz span, about ten octaves, and +1.0 oct is a musical starting point. Negative depth inverts the source.

Curve, Linear is no shaping. Exp boosts the top of the source’s range, Log the bottom, S-curve softens both ends. Bipolar recentres a one-sided source (envelope, ADSR, macro, velocity, pitch, Link level) to swing both ways around the knob.

The response screen shades each cutoff's sweep range, the knobs draw a ghost ring showing the live modulated value, and each source tab lights while its source is routed. Hover a modulated knob and the tooltip lists what is modulating it.

Mod-of-mod: route a very slow, free-running LFO 3 to LFO 1's rate and the wobble wanders; route it to LFO 1's depth and the wobble breathes. Rate can only be bent on a free-running LFO, since a synced one stays on the grid by design.

Modulation is evaluated every 32 samples, so a 1/32 sequence at a 1024-sample buffer still lands on the grid, and a square LFO has clean edges at any buffer size.

The Sources

LFOs

Four identical LFOs, one per tab: free-running or tempo-locked, with a drawable custom shape.

Shape, Sine, Triangle, Saw, Square, Random, S&H or Custom. Random gives a smooth new value each cycle, S&H steps on every subdivision, and Custom opens the waveform editor.

Rate, 0.01 to 20 Hz in Free mode. With SYNC on, musical divisions from 1/64 to 8 bars, with the effective Hz printed under the selector.

Sync / Feel / Swing, Locks the rate to the host tempo. FEEL multiplies the division by two thirds or three halves for triplet or dotted, and SWING delays the off-beats. A synced LFO stays on the grid through transport jumps.

Mode, Loop, One-Shot (fires once per trigger), Ping-Pong (reverses each cycle) or Reverse.

MIDI Trig, Resets the phase to zero on every MIDI note.

Phase, 0 to 360 degrees. Offsets a synced LFO against the grid, or two LFOs against each other.

Unipolar, The LFO runs 0 to 100 percent instead of −100 to +100, so a route pushes its destination one way from the knob, like an envelope.

Depth, The LFO’s overall amount before any route’s depth. Itself a mod-of-mod destination.

The waveform editor. With SHAPE on Custom, drag the handles to draw a Bezier curve. Double-click adds a point, right-click or Cmd-click removes one. The drawing is saved with the preset exactly as drawn.

Env Follower

Turns a signal's level into a source. SOURCE chooses what it listens to: Main (the track), External (the host's sidechain bus), or Link A to D (another track over Orra Link). DETECTOR is Peak (snappy) or RMS (smoother, ignores clicks), and detection reads the louder channel. ATTACK (0.1 to 500 ms) and RELEASE (1 ms to 5 s) shape the response. THRESHOLD gates out the noise floor and rescales above it, so raising it never lowers the envelope's ceiling. OUTPUT trims the envelope before the matrix. LISTEN band-limits what the follower hears with FREQ and Q, so you can sit it on the kick at 60 Hz or a vocal at 2 kHz. The audio you filter is untouched.

Seq

A 16-step sequencer locked to the host grid. Drag the bars to draw each step's value, and Alt or Opt-drag a bar to set its probability, the chance it plays; a skipped step holds the previous value. Right-click the strip for pattern tools: zero, clear, invert, reverse, shift and randomise. RATE (1/64 to 8 bars) and FEEL set the step length; STEPS (1 to 16) sets the pattern length, and odd lengths against 4/4 make evolving polyrhythms. SWING delays every second step. MODE is Loop, One-Shot (a MIDI note restarts it), Ping-Pong, Reverse or Random. GLIDE slews between steps: a hard step on a resonant cutoff can pop, and 4 percent is enough to remove the click while still sounding stepped. Factory presets and DICE never go below it.

ADSR

A triggered envelope. TRIGGER is MIDI (note-on starts it, note-off releases), Audio (a transient above SENS starts it, release when it fades), or both. ATTACK, DECAY, SUSTAIN and RELEASE are the stages; CURVE bends all of them, from logarithmic (fast start, slow finish) to exponential (slow start, snappy finish). VELOCITY sets how much the note's velocity, or the transient's strength, scales the peak. Audio triggering re-arms quickly enough for dense hi-hats, and SENS is relative to the raw input before the IN gain. Put the ADSR on a cutoff with Audio trigger and every hit plucks the filter open with no MIDI in the project.

Filter FM & The Spectral Circuit

Filter FM

The FM keycap on a filter card opens a small panel that modulates that cell's cutoff at audio rate, giving metallic, vocal and bell-like colours no LFO can reach. It works on the Moog, SVF, Diode, MS-20 and Comb circuits, and the keycap stays lit while the amount is above zero.

Amount, FM depth, up to ±3 octaves of cutoff swing. It is a modulation destination itself, so drop an envelope on it and the FM only appears on hits.

Source, Oscillator: an internal sine at RATIO times the tracked note, with key tracking on, or the cutoff. Input: the signal being filtered modulates its own filter.

Ratio, 0.25x to 8x. Whole numbers stay harmonic; in-between ratios go clangorous. The knob snaps to musical ratios while dragging, and holding Alt gives a free value.

The Spectral circuit

Choose Spectral as a cell's circuit and the SHAPE keycap opens a drawing window: the filter's magnitude across five octaves either side of the cutoff. The centre line is unity, the top is +12 dB, the bottom −60 dB. Drag the points to draw, double-click to add or remove one, and Cmd or Ctrl+Z undoes. LIBRARY loads a starting shape, either Lowpass, Highpass, Bandpass, Notch, Tilt Up, Tilt Down, Bell, Twin Peaks, Ripple or Stairs, or a fresh random one to draw on.

Once drawn, the shape behaves like any other filter: CUTOFF slides it along the frequency axis, RESONANCE adds a peak at the cutoff, and key tracking and LFOs move it. It is an STFT filter, so it is linear-phase and adds about 17 ms of latency, reported to the host and identical at every sample rate. The drawing is saved with the preset and copied with the cell.

Right-click either filter card for Copy F1 to F2, Swap and Reset. All three are single undo steps.

Presets, Banks & Undo

The preset browser

Click the preset name in the header and the browser opens over the plugin: a BROWSE column (All, Favourites, Factory, User, then every category that has presets), the preset list, and an INFO column with the author, tags and notes. Click a preset to load it, auditioning is instant, and Cmd or Ctrl+Z undoes a load. The up and down arrows step through the list, and the search box filters by name, tags, notes or category as you type. Click the star at the left of a row to mark a favourite, factory presets included. Esc closes.

Along the bottom: INIT (back to the transparent Default), SAVE (overwrite the current user preset), SAVE AS (a new preset with a name, category, tags, author and notes), RENAME, DELETE, IMPORT (a preset file from anywhere), EXPORT (write the current sound to a file to share) and REVEAL (show the file in the Finder or Explorer).

Forty-four factory presets ship in seven categories, Sweep, Rhythmic, Vocal, Texture, Bass, FX and Utility, and every one has a note explaining what it is for. User presets are stored one folder per category in ~/Library/Application Support/Orra Audio/Orra Filter/Presets on macOS and %APPDATA%\Orra Audio\Orra Filter\Presets on Windows, as plain files you can copy between machines.

Link A to D picks are not saved in presets, since they are track names of one song, and neither is the 2X / 4X setting. Both ride the session.

A/B/C/D banks

Four snapshot banks for comparing settings. Click a bank to switch and the outgoing bank saves itself first, so there is nothing to store by hand. A dot on the keycap marks a bank with content, Alt or Opt-click copies the current state into a bank, and the keys A, B, C and D switch banks while S resets the active one (it asks first). The active bank and all four snapshots are saved with your session, each with its own preset name and edited dot. Park a starting tone in A, branch into B, compare with a click.

Undo

UNDO and REDO in the header, or Cmd/Ctrl+Z and Cmd/Ctrl+Shift+Z, step back through knob moves, routes, DICE rolls, RESET, preset loads and drawn shapes. Host automation is not recorded. Forty steps deep.

DICE

The DICE key throws a complete, musical patch (filters, routing, LFOs, sequencer, ADSR, envelope follower and macros) in one undoable step. It never touches gain staging, dry/wet, bypass, OSC or global settings, never lets a filter self-oscillate, and always wires Macro 1 to something worth turning, so a roll is playable the moment it lands.

Every roll is built from a recipe: a musical archetype that decides which sections and sources belong together, instead of a random soup. By default the dice picks a recipe at random; right-click DICE to lock it to one.

Pluck

An audio- or MIDI-triggered ADSR snapping a resonant low-pass open on every hit, sometimes with key tracking. Macro 1 opens the filter.

Talker

A Formant, or Resonator, with a slow vowel sweep and the follower pushing the resonance. Macro 1 is the vowel.

Rhythmic

The step sequencer, with probabilities, swing, glide and a playback mode, driving the cutoff, plus a synced unipolar LFO on resonance or morph.

Dub Sweep

A one- to eight-bar LFO on a driven low-pass, the follower on resonance, a comb or high-pass in the second cell, analog drift and stereo spread.

Drift

Everything free-running and slow: analog on, wide stereo, and LFO 3 and 4 bending LFO 1’s rate and depth so nothing ever repeats.

Chaos

Any shape, mode and rate, sometimes filter FM, four to seven routes with curves. Wild, but bounded.

The right-click menu also lets you keep sections as they are, whether filters, routing or modulation, so a roll only reshuffles the rest. Hover DICE to see the last recipe rolled. The preset name stays and the edited dot appears, so a roll is an edit of what you loaded rather than a new patch: park a keeper in a bank first and roll into another.

Keyboard & Mouse

Double-click a knobReturn to default. Double-click its value to type an exact number.
Shift-dragFine adjustment on every knob.
Right-click a knobQuick-assign menu: add or edit modulation.
A / B / C / D, SSwitch bank; reset the active bank (it asks first). No modifier.
Cmd/Ctrl+Z, +Shift+ZUndo, redo.
Alt/Opt-drag a stepSet that step’s probability. Alt on FM RATIO gives a free ratio.
Right-click the tips keyTooltip language: English, Dutch, Japanese, Spanish, Portuguese, German, French.

Tips & Workflow

Start from Default, or from a roll

A fresh insert is transparent, with Filter 1 wide open, Filter 2 off and nothing moving, so the plugin never changes a track just by being there. When you want a starting point fast, press DICE and keep what lands.

Drag, don’t dig

The matrix is there when you want it, but a route is one drag: LFO tab onto CUTOFF, MACRO label onto MORPH, ENV tab onto RESONANCE. The callout that opens is the whole route.

Let the audio play the filter

AUDIO key tracking on a bass or a vocal makes the cutoff follow the melody with no MIDI. Add the ADSR with an Audio trigger on the cutoff and every note plucks. Add a little PORTAMENTO for slides.

Series for band-pass with two edges

A Moog low-pass into an SVF high-pass in Series gives a band-pass whose two edges you control separately: sweep one, hold the other. Telephone and radio effects are exactly this.

Read the screen

The curves include phase. If the white combined line dips where you did not expect, that is a cancellation between the cells or against the dry signal, useful for allpass phasers, worth checking in parallel mixes.

Keep 2X on for drive and resonance

At 44.1 and 48 kHz, drive on the ladders aliases audibly without oversampling. 2X, the default, removes it at a modest CPU cost, and 4X is there for the hottest settings. The 49- or 91-sample latency is reported and phase-true, so a parallel dry/wet blend stays clean.

Glide the sequencer a little

A hard step on a resonant cutoff clicks. GLIDE at 4 percent removes the click and still sounds stepped; factory presets and DICE never go below it.

Banks for decisions, undo for mistakes

Park a candidate in A, branch into B and push it further, compare with a click. Cmd or Ctrl+Z steps back through everything including DICE rolls and preset loads.

Activation & Licensing

The first time you open Orra Filter on a machine it needs to be activated. Click the ORRA FILTER wordmark at any time to open the licence and info panel.

14-day demo, run the full plugin, unrestricted, before deciding.

Activation, paste the licence key from your purchase confirmation. Activation is shared by every open instance within two seconds, so you only enter it once.

Once activated the plugin works offline; it only re-checks the licence when it can reach the internet, and a failed check never locks you out. To move a licence to another machine, open the licence panel and choose Deactivate, which frees the slot to activate elsewhere.

Need a hand?

If anything here did not answer your question, our support team is happy to help.