1. Start here

ATROPA keeps a complete synthesizer surface visible while giving every layer its own signal path. Start with a factory preset, then move through the signal flow from left to right.

The header provides preset navigation, A/B comparison, Randomize, the account entry, window size, polyphony, quality controls and PANIC. The main page buttons are LAYER 1–4, EFFECTS, ADVANCED, and MATRIX.

2. Install & first launch

System requirements

Use a current 64-bit AU or VST3 host. AAX is not part of the v1.0.0 distribution. The installer packages are separate for ATROPA Synth and ATROPA FX.

Install locations

First launch checklist

1. Install the package for your OS and restart the host if it was open during installation.
2. Create a new instrument track and choose ATROPA. For an effect-only track, choose ATROPA FX when your Premium subscription is active.
3. Play a MIDI note. Layer 1 is enabled by default; the other layers start silent.
4. Click the current preset name and load a Factory preset. If the host does not scan the plug-in, run its plug-in rescan.
5. Set the host buffer before designing: 128–256 samples is a useful starting point, then raise it for large unison/EFX patches.

3. Interface & gestures

Pages and layer tabs

• LAYER 1–4: choose which layer’s OSC, Filter, Amp and envelope controls are edited.
• EFFECTS: open the modular rack and the selected effect’s controls.
• ADVANCED: open render quality, sampler pitch and analyzer settings.
• MATRIX: view and edit the 16 modulation routes.
• OSC 1 / OSC 2 / SUB / COMMON: switch the source subsection within the selected layer.
• FILTER 1 / FILTER 2: switch filter controls; the selected filter’s graph follows.
• AMP ENV / FILTER ENV: edit the selected layer’s envelopes.
• ENV / LFO 1–3 / STEP / MIDI: switch the global modulation subsection.

Common gestures

Window size and panic

WINDOW SIZE offers 80%, 100% and 125%. This is an editor preference and does not dirty a preset or DAW session. PANIC sends internal All Notes Off / All Sound Off behavior, releases the on-screen keyboard, centers the pitch wheel and clears stuck voice state.

4. Presets

Click the current preset name to open the browser. The header also provides previous/next preset buttons, A/B comparison and a dice button for controlled randomization.

Browser actions

A/B and Randomize

A and B are comparison slots. ATROPA captures the current slot before switching, so you can compare two sound states without saving first. The dice button randomizes the selected layer and global modulation only; layer enable state, pan, filter parallel pan, Matrix assignments and the EFX chain are preserved.

5. Layers & voice architecture

ATROPA has four independent layers. Layer 1 is enabled on a new instance; Layers 2–4 are available but start at 0 oscillator level. Click the layer tab to edit it and its LED to enable/disable its audio path.

Global voice controls

POLY selects 8, 16, 24 or 32 maximum voices. MONO switches to monophonic operation. NOTE PRIORITY is Newest, Oldest, Highest or Lowest. PITCH BEND RANGE is 1–24 semitones. GLIDE TIME is 0–2 seconds and GLIDE MODE is Always or Legato.

Copy a layer

Right-click a layer tab or enable LED, choose COPY TO, then choose the destination layer. Synthesis parameters and oscillator WAV assignments are copied; the destination’s layer enable state is not changed.

6. Oscillators & sound sources

OSC 1 and OSC 2

Each layer has two main oscillators. Choose Sine, Triangle, Saw, Square, Pulse, MultiSaw, WT or SAMPLER.

MultiSaw

Unison is 1–8 saw voices, DETUNE spreads them by 0–100 cents, and PHASE RESET chooses whether voices restart together at note-on or continue their phases.

WT and SAMPLER

Choose WT or SAMPLER and click LOAD WAV. AUTO PITCH analyzes a stable source pitch and writes the detected root note; the root can be edited from MIDI note 0–127 with fractional cents.

WT playback is always cyclic. SAMPLER offers ONE SHOT or LOOP. In ADVANCED → SAMPLER PITCH, RESAMPLE changes duration with pitch, while FIXED LENGTH keeps source duration and loop period while shifting pitch through overlap-add playback.

SUB, Noise and Punch

SUB offers Sine, Square, Saw and OSC1 Same, with ±24 semitones and independent level. Noise is White or Pink with independent level. Punch is a short transient source with independent Level and 0.5–20 ms Decay.

FM, AM and sync

7. Dual filters

Every layer has Filter 1 and Filter 2. Set ROUTE to SERIAL (F1 → cascade drive → F2) or PARALLEL (the source is split into F1/F2). Parallel Pan is active only in Parallel mode.

Core controls

Formant and cascade drive

When a Formant model is selected, VOWEL morphs the vowel response and LOW BOOST restores low-frequency weight. In Serial mode, cascade drive offers 15 algorithms: Tube Sat, Diode Clip, Ge Clip, Fold Si, Fold Schottky, Fold Ge, Tape Sat, Crunch, Soft Clip, Hard Clip, Sine Fold, Tri Fold, Saw Fold, Bit Crush and Decimator.

8. Envelopes

Envelope time knobs use a musical, non-linear mapping rather than a raw 0–1 display. Positive and negative slope values reshape the curve without changing the endpoints.

AMP ENV (Env 1)

The selected layer’s amplifier envelope has ATTACK, DECAY, SUSTAIN, RELEASE, independent A SLOPE and D SLOPE, and INVERT. Layer ranges are Attack 0–5 s, Decay 5 ms–5 s, Sustain 0–100% and Release 2 ms–12 s.

FILTER ENV (Env 2)

Filter ENV has the same ADSR and slope controls, a bipolar DEPTH (−100…+100%) and an F1/F2 target switch. Double-click DEPTH returns to neutral 0%. Its depth is applied to the selected filter cutoff.

Global ENV

The global ENV tab has Attack, Attack Slope, Decay, Decay Slope, Sustain, Release, Depth, Target and Invert. It is a modulation source for synthesis and EFX targets; its release mapping is approximately 10 ms–10 s.

9. Modulation

LFO 1–3

Each global LFO offers Sine, Triangle, Saw, Ramp, Square, Pulse, S&H and Rand. Select an LFO with the LFO selector, then set:

Macros and XY

Six Macros and the XY X/Y pad are modulation sources. Rename Macro labels by double-clicking; names travel with the patch state. Macro values are 0–100% and are available to Matrix routes.

StepGate

The global STEP source is an 8- or 16-step modulation generator. Set Run Mode to Free Run, DAW Sync or Note Sync; Free Rate is 0.05–30 Hz; Gate is 0–100%; Multiplier is x0.5, x1 or x2; each step is 0–127; TIE joins a step to the next. 12 TONE quantizes the output to 12-TET without rewriting the stored step values.

10. Modulation Matrix

MATRIX contains 16 slots. Each slot stores Source, Target, bipolar Amount, Bipolar mode, Layer scope and Mute state. Routes are part of the patch and DAW session state.

Fast assignment

Drag an exposed + SOURCE button onto an assignable parameter. The v1.0.0 drag shelf exposes LFO 1–3, Env 1–3, Velocity, Aftertouch, Mod Wheel, MIDI CC 1–4 and StepGate. The Matrix source menu also includes Macros, XY X/Y, Note and Env Follower.

Editing a slot

11. Effects chain

Open EFFECTS to build a modular rack. Click + ADD EFX to add a launch processor, click a card to edit it, use ON/OFF to bypass it, X to remove it, and drag cards horizontally to reorder. The global ALL EFX switch bypasses the whole chain while preserving each module’s individual ON state.

At v1.0.0, the public rack contains 13 Included processors and three Premium processors. Premium processors show their access state and can be previewed when eligible.

12. Account & Premium access

The core ATROPA instrument is free. Sign-in is required to sync purchases, refresh entitlements and use verified offline access. Payment details are entered only in the secure SoundRave/Stripe browser pages; the plug-in never stores card information.

Sign in and refresh

1. Click OPEN ACCOUNT / LICENSE (or the account button) in the ATROPA header.
2. Enter the email and password for your SoundRave account, then click SIGN IN. CREATE ACCOUNT opens the secure registration page in the default browser.
3. After a purchase or subscription change, click REFRESH LICENSE. Checkout success pages alone do not unlock an effect; the signed entitlement must be refreshed.
4. Use BILLING & PLAN for subscription management and SIGN OUT to revoke the local session.

Premium states and 10-minute previews

Premium EFX can show AVAILABLE, OWNED, INCLUDED IN SUBSCRIPTION or LOCKED. A published, unowned Premium EFX can be tried for 10 continuous minutes. When the preview ends, that effect enters a 24-hour cooldown; each effect has its own independent timer. A ready preview starts when the effect is added/enabled. An effect in cooldown can remain in the rack bypassed and can be enabled after the timer ends.

Offline behavior and privacy

• Access tokens remain in memory only.
• A refresh token is stored per user in a protected SoundRave/ATROPA application-data file (Windows uses the OS credential store).
• The offline cache contains only a signed entitlement envelope; the plug-in re-verifies it before granting access.
• Verified offline access continues until the envelope’s offline validity/grace window ends. Reconnect and use REFRESH LICENSE if access expires.

13. Advanced & quality

Quality, analyzer resolution and editor window size are preferences rather than musical sound data. They are not included in an exported .atropapreset.

14. MIDI & performance

Direct MIDI assignments

The MIDI page provides a target and bipolar depth for Velocity, Aftertouch and Mod Wheel. Four assignable lanes (CC A–D) add a MIDI CC number 0–127, target and bipolar depth.

Keyboard and wheels

The on-screen keyboard sends internal note events. The GUI pitch wheel sends the full 14-bit range (0–16383) and returns to center through PANIC. The modulation wheel sends MIDI-style values 0–127.

Master

MASTER controls final output level. TUNE provides ±12 semitones of global tuning adjustment. A host tempo is used by DAW-synchronized LFO, StepGate and tempo-aware EFX divisions.

15. Sessions, automation & files

DAW sessions and automation

Sound parameters, Matrix routes, Macro names, layer state and the EFX rack state are stored in the host session and can be recalled with the plug-in. APVTS parameters support host automation. Editor window size, page selection and render-quality preferences are intentionally separate from sound presets.

User preset format

.atropapreset is UTF-8 pretty-printed JSON. It stores product/format metadata, plain parameter values, categories, Macro names and safe WAV references. Enum values are validated; invalid or out-of-range data is rejected, and unknown parameter IDs are ignored for forward compatibility.

File limits and portability

Imports accept individual files up to 4 MB and folder batches up to 2048 files. User WAV references under the home/Documents folders are portable; absolute paths outside those locations are omitted on export. Keep shared WAVs in a stable project folder and save the preset again after relinking.

16. Troubleshooting

17. Quick reference

Keep this page close

For a fast sound-design pass: load a Factory preset, enable a second layer, choose OSC 1/2 waves, set Filter Route and CF SYNC, shape AMP ENV, drag an LFO source to a target, then add and reorder EFX. Save the result with SAVE AS… before experimenting with Randomize.