On a mono source, push SPREAD high — AURORA turns it into a wide, crystalline stereo image without the comb-filtering you'd get from a Haas widener.
What AURORA is
AURORA is a spectral stereo widener. It splits your sound into frequency bands and sends each one to a different place in the stereo field — lows in the center, highs fanning out to the sides, or whatever frequency-to-position curve you draw. The trick that matters: it does this by relocating the spectrum by per-bin phase de-correlation, not with a Haas delay that falls apart in mono. The result is a huge, crystalline width that still sums cleanly.
Where it shines It shines on synths, pads, plucks, layered guitars, vocal doubles and full submixes that need to feel wide without smearing — and on anything that has to survive a mono fold-down. It's the most mix-tool of the catalog: real width, not a color effect. Default settings already sound; just reach for it when something needs to open up.
Up and running in five steps
- Drop AURORA on a stereo (or mono) track — or on a bus to widen a whole group.
- Bring SPREAD up until the spectrum fans across the field (55 % is a musical start).
- Use TILT to set the character: 0 keeps lows centered and highs at the edges; pull it negative to lean the width into the lows and rein the air toward the center.
- If the lows get loose, raise MONO SAFE to pin the bass back to the middle.
- Optional groove: turn SYNC on, pick a division, and raise MOTION so the fan breathes in time with the track.
How the signal moves through it
The dry signal feeds an STFT engine (overlap-add, Hann at 75 % overlap, 2048-point window). Each frequency bin is assigned an azimuth by the frequency-to-position curve (set by TILT) scaled by a global angle (SPREAD); its magnitude is split L/R by a constant-power law and its phase is de-correlated per bin (opposite in L/R) — ultra-wide stereo with no comb-filtering and no mono collapse. MONO SAFE collapses the bins below a cutoff back toward center so the bass stays mono-compatible; MOTION slowly opens and closes the fan (capped under ~20 Hz to avoid audible AM, and locked to the host when SYNC is on); DUCK is an internal sidechain that pulls the whole fan toward center when the dry transient hits and lets it reopen in the gaps. Finally a zero-latency limiter keeps the output clip-safe before MIX blends wet against the latency-aligned dry.
Every control, explained
FREE / SYNC
The tempo mode for MOTION — free-running or locked to the host.
Toggle on the left rail. FREE exposes the RATE knob in Hz; SYNC replaces it with the DIVISION chips and follows your project tempo.
Leave it on FREE for a slow cinematic drift; switch to SYNC when you want the fan to pulse with the groove.
RATE
Free-running speed of the MOTION fan, in Hz.
0.02–8 Hz (default 0.3), mapped logarithmically so every step feels even. Only visible in FREE mode.
Stay well under 1 Hz for a wide, breathing motion; the engine caps the angle under ~20 Hz so you never get audible tremolo.
DIVISION
The tempo-synced cycle length of the fan.
Chips: 1/4 · 1/2 · 1 BAR · 2 BAR (default 1 BAR). One full open-and-close per cycle. Only visible when SYNC is on.
1 BAR reads as obvious, musical movement; 2 BAR is a slow hypnotic sweep that sits under pads.
SPREAD
How far the bands fan out — the master width of the effect.
0–100 % (default 55). Scales the angle assigned to every bin: 0 % is mono (everything centered), 100 % is the maximum spectral spread.
55–75 % is the sweet spot for a wide-but-believable image; push to 100 % only when you want it huge.
TILT
The frequency-to-position curve — the shape of the aurora.
−100…+100 (bipolar, default 0). At 0, lows sit center and highs open to the edges; negative reins the air toward the center and leans the width into the lows; positive opens earlier in frequency.
Default 0 is the 'correct' map (lows mono, highs wide). Go negative to darken the image — air to the center, width in the low-mids.
MOTION
Slowly opens and closes the fan over time.
0–100 % (default 0, off). Modulates the global spread so the aurora breathes; its speed comes from RATE (FREE) or DIVISION (SYNC). Movement is held under ~20 Hz so it never turns into AM.
A little (20–40 %) adds life; pair it with SYNC and a 1 BAR division to make the width groove with the track.
MONO SAFE
Pins the low end to the center for mono compatibility.
0–100 % (default 0). Sets the cutoff below which bins collapse toward center. ILD is ineffective under ~1 kHz, so widening down there only risks the mono sum — this protects it.
Raise it when the material has strong low-mids to protect. A hard sub floor is always mono regardless, so the kick stays solid.
DUCK
Makes the width breathe with the performance.
0–100 % (default 0, off). An internal sidechain follows the dry envelope and pulls the fan toward center when the transient hits, reopening it in the gaps. Acts on the global angle only — never on the phase.
On a drum loop, 30–50 % closes the width on each hit and reopens between them — the field reacts instead of masking the punch.
MIX
Dry/wet blend of the effect.
0–100 % (default 100, constant-power law). At 100 % you hear the fully spread signal; lower it to keep a dry center anchor. The dry is delay-aligned to the wet so there's no phase cancellation.
Keep 100 % on an insert for full width; pull back to 50–70 % when you want presence and width together.
IN / OUT
Input and output trim.
−24…+24 dB each (default 0). Stage gain into the STFT engine and compensate the level on the way out.
Trim IN down a touch on hot signals so the DUCK detector reads transients cleanly.
IN PHASE
Chassis mono-safety — collapses the widener to a mono-compatible path.
Toggle in the utility column. One click forces the engine to fold its widener so nothing cancels when summed to mono; the chassis sums the lows to mono after.
Leave it on as a safety net when the track absolutely has to translate on a phone speaker or club PA.
Tips & tricks
01
02
For a moving width that grooves, turn SYNC on, pick 1 BAR, and bring MOTION to ~40 % — the fan opens and closes locked to the bar.
03
Use DUCK on a busy submix: the width steps back on every transient and reopens in the gaps, so the effect sits in the mix instead of masking it.
04
Negative TILT leans the image dark — the air reined toward the center, the width sitting in the low-mids — a signature colour for leads while MONO SAFE protects the bottom.
05
On a master or stereo bus, keep MONO SAFE up and SPREAD moderate (40–60 %) for safe, translatable width that won't collapse on phones.
06
Automate SPREAD from 0 to 80 % across a build — the sound literally unfolds across the field as the drop arrives.
Troubleshooting
The low end gets loose or smeary when I widen.
Raise MONO SAFE to pin the bass back to center. Stereo width below ~1 kHz doesn't read as direction and only risks the mono sum — keeping lows centered is the intended, correct behavior.
It sounds thin or loses body when summed to mono.
Click IN PHASE and/or raise MONO SAFE. AURORA's per-bin de-correlation is mono-aware, so it sums far better than a blunt mid-side widener, but very high SPREAD on full-range material is safest with the mono path engaged.
There's a slight delay / the plugin reports latency.
That's the STFT block latency (2048 samples at 44.1/48k, 4096 at 96k). It's declared honestly to the host, so PDC keeps everything aligned. It's the trade for real spectral relocation — a mid-side widener has none, but it can't do this.
MOTION feels static or won't follow my tempo.
Make sure SYNC is on and a DIVISION is selected — in FREE mode the fan runs at the RATE knob in Hz and ignores the host tempo. Also raise MOTION above 0; at 0 it's off and the width is fixed.
Specs
Formats: VST3 · AU
Systems: macOS
Build: Universal (Apple Silicon + Intel)
Engine: STFT spectral panning (overlap-add, Hann 75 %)
Window: 2048-point (4096 @ 96k)
Bands: 24-band visual readout · phase-decorrelated
License: AGPLv3 · open-source