#gFractor — User Manual

This is the end-user manual for gFractor 1.2.0, a multi-mode spectrum analyzer, oscilloscope, waterfall, and metering plugin from GrowlAudio. It assumes you're an audio engineer or producer who already knows what FFT, mid/side, slope tilt, transients, and phase correlation are.

#1. What gFractor is

A measurement plugin (VST3 / AU / Standalone) you put on any bus to see what's in your audio. It offers three views — a spectrum analyzer, a tempo-synced oscilloscope, and a scrolling waterfall (reassigned spectrogram) — over four channel decompositions (Mid/Side, Left/Right, Tonal/Transient, and L+R mono-sum), with a goniometer + correlation + width-per-octave metering panel and a full ITU-R BS.1770-4 LUFS meter alongside. It does not colour the audio unless you tell it to: a gain stage, a dry/wet mix, and an audition bell filter are the only signal-path controls.

Insert it post-fader on a master bus or any group whose tonal/stereo balance you want to monitor.

#2. Quick start

1. Load gFractor on a bus and play audio.
2. Two coloured spectrum curves animate in real time. By default:
   • Green is the Primary channel (Mid in M/S mode, Left in L/R, Transient in T/T).
   • Amber is the Secondary channel (Side, Right, or Tonal).
3. Press Tab to cycle the channel decomposition: M/S → L/R → TRN → M/S… The pill captions in the footer rename themselves to match (MID|SIDE, LEFT|RIGHT, TRANS|TONAL). The fourth mode, L+R mono-sum, is selected from the footer Mode dropdown (Tab cycles only the first three — see section 3).
4. Press V to cycle the view: Spectrum → Oscilloscope → Waterfall → Spectrum…
5. Click STEREO in the footer to slide out the right-side metering panel (goniometer, correlation, width-per-octave). Click LUFS for the loudness meter. (Only one of the two can be open at a time.)
6. Hover the spectrum to read frequency / dB / nearest musical note. Right-click and drag to audition a bell filter (drag vertical for Q).

That's the whole product, conceptually. The rest of this manual explains each piece.

#3. The Primary / Secondary concept

gFractor's most important UI decision: the same two channel toggles, the same two curves, and the same two colours are reused across all channel modes. They are always labelled Primary (green) and Secondary (amber) internally — only the captions change.

A few consequences:

• Keys 1 and 2 toggle the visibility of the green and amber traces — they only affect what you see, not what is heard. To actually mute a channel from the audio path, use Shift+1 (Primary) and Shift+2 (Secondary).
• In L+R mode there is only one lane: both channels are summed into a single Primary trace and the Secondary pill is hidden. Useful for a quick mono-compatibility check or a clutter-free view.
• The Reference / Ghost / Target overlays use different colours (blue and pink) to avoid collisions, so you can run a reference comparison without losing track of which curve is which.

About Tab: the keyboard cycle steps through the first three modes only (M/S → L/R → TRN). To reach L+R, pick it from the footer Mode dropdown.

The T/T mode is worth a separate note: it uses a dual-envelope tracker (fast vs slow envelope, normalised by body level). The Transient curve emphasises percussive content; the Tonal curve emphasises sustained content. Adjust the time constant in Preferences → Analyzer → Trans Len (default 1.0 ms; range 0.1–10 ms).

#4. Interface tour

      +-------------------------------------------------------------+
      |  HEADER     g/Fractor • by GrowlAudio  [Preset][SETTINGS][Help]
      +-------------------------------------------------------------+
      |                                                |            |
      |                                                | Stereo /   |
      |  VIEW AREA   Spectrum / Oscilloscope /         | LUFS panel |
      |              Waterfall                          | (sliding)  |
      |                                                |            |
      +-------------------------------------------------------------+
      |  FOOTER    [SPEC▾] [M/S▾] [MID] [SIDE]  [REF] [GHOST] [FREEZE]
      |            (spectrum) [HOLD] [SAVE] [LOAD] [TARGET]          |
      |            [LUFS] [STEREO]                                   |
      +-------------------------------------------------------------+
      |  HINT BAR  hover hints       [FFT▾][Ovr▾][Dec▾][Slp▾][Smo▾] |
      +-------------------------------------------------------------+
      

#Header bar

• Preset pill — shows the current preset name, with a dot if the state is dirty. Click for the preset menu.
• SETTINGS — opens the Preferences overlay (section 10).
• Help — About, Check for Updates, link to this Manual, and (in standalone) Audio Settings. A small dot on the button means a newer gFractor version is available.

#View area

The main display. One of three views renders here — Spectrum, Oscilloscope, or Waterfall — cycled with V or the footer view dropdown (SPEC / SCOPE / WTF). Press W in spectrum mode to expand the view fullscreen across the footer/hint bar.

#Footer bar

The control surface. Most footer pills are toggles; a few (View, Channel Mode, Vertical Scale, Time Window, and the Waterfall pills) are dropdowns. Pill captions on the left depend on channel mode; pill availability depends on which view is active — spectrum, oscilloscope, and waterfall each show their own set.

#Hint bar

The bottom strip is contextual: hover over any control or the spectrum/scope itself, and the hint bar shows what you can do there (e.g. CLICK | DRAG — Audition band | Move between bands). On the right, in spectrum mode, you also get five global dropdowns for FFT size, Overlap, Decay, Slope, and Smoothing.

#Right-side panels

The Stereo and LUFS pills each slide out a panel on the right edge. They share the right column, so only one can be open at a time — opening one closes the other. Drag the vertical divider on the left edge of the panel to resize.

#5. The Spectrum view

A real-time FFT magnitude spectrum, log- or linear-frequency × dB, with 256 log-spaced render points across the visible range. Both Primary and Secondary curves are drawn simultaneously and can be overlaid with Ghost (sidechain) and Reference (frozen capture) curves.

#Analysis parameters (hint-bar dropdowns)

The frequency scale (Log or Linear) is set in Preferences → Analyzer → Freq Scale, not the hint bar. Log is the classic view; Linear is handy for inspecting harmonic spacing.

#Persistence controls (footer)

• FREEZE (key Z) — pauses the display without stopping audio analysis. Useful for taking a screenshot of a transient. Freeze applies to whichever view is active.
• HOLD (key H) — infinite peak hold. Adds a glow trace at the maximum bin levels seen since enabled. Disable + re-enable to reset.
• GHOST (key G) — shows a faded "now" copy of the spectrum even while frozen, so you can compare a captured moment against live audio.

#Reference, Target, Audition

• REF (key R) — analyses the sidechain input and overlays it in blue (Primary) and pink (Secondary). See section 8 for routing.
• TARGET (key T) — overlay a saved EQ curve loaded from disk. Use LOAD to import; SAVE captures the current Primary curve as a target file you can reload later.
• Right-click drag on the spectrum — auditions a resonant bell filter on the audio path at the cursor frequency. Horizontal drag sweeps frequency, vertical drag adjusts Q (0.5–10, default 4). Release to remove. Useful for confirming a resonance by ear.

#Band audition strip

Just above the frequency axis, gFractor draws a thin clickable strip with seven musical band labels: Sub (20–80 Hz), Low (80–300), Low-Mid (300–600), Mid (600–2000), Hi-Mid (2000–6000), High (6000–12000), and Air (12000–20000 Hz). Audition a band to hear a problem frequency in isolation:

• Click a band to solo it (band-pass) while the mouse is held.
• Cmd-click (macOS) / Ctrl-click (Windows/Linux) to latch the band so it stays active after you release.
• Right-click a band to cut it instead — a notch (band-reject) rather than a solo.
• Drag along the strip to move between bands without releasing.

Solo and cut are visually distinct — a blue accent with solid boundaries for solo ("keep"), a warm red with dashed boundaries for cut — and the styling is colour-blind friendly. The strip can be hidden with Preferences → Display → Band Hints.

#Split spectrum

Press X in spectrum mode (or toggle Preferences → Display → Split Spectrum) to stack the channels — Primary in the top half, Secondary in the bottom half — so you can compare them without overlap.

#Fullscreen

Press W to hide the footer + hint bar and expand the spectrum across the entire window. Press W again or Esc to restore.

#6. The Oscilloscope view

Press V until the oscilloscope shows. Tempo-synced time-domain waveform of Primary and Secondary, with the cursor tracking DAW playback position.

An optional CRT filter (Preferences → Display) gives the trace a warmer, more analog feel, paired with a denser grid graticule.

#Pan and zoom

• Mouse wheel over the scope — horizontal zoom.
• Horizontal drag — pan the time window when zoomed in.

#Ghost / Reference in the scope

GHOST and REF work in the oscilloscope too: they overlay the sidechain signal as ghosted traces on top of the main waveform. Useful when comparing pre/post processing on the same musical moment.

#7. The Waterfall view

Press V until the waterfall shows — a scrolling reassigned spectrogram. Energy is snapped to its true time–frequency location, so a pure tone paints a single crisp line instead of a smeared band, making harmonics, sidebands, and transients far easier to read. Frequency runs along one axis, time scrolls, and level is mapped to colour (range fixed at −100 to 0 dB).

The waterfall has its own footer pills (the channel-mode controls are hidden in this view):

The shared FREEZE (key Z) pauses the waterfall so you can study a moment in detail.

#8. Reference mode (sidechain A/B)

Reference mode lets you A/B against any signal routed to gFractor's sidechain input. When enabled, that signal is analysed in parallel with the main input and drawn as blue/pink curves over the green/amber ones.

#Routing the sidechain

#Using reference

• REF (key R) — latching toggle.
• Hold Ctrl — momentary reference: REF is on only while held. Useful for fast A/B without taking your hand off the keyboard.

The reference signal does not pass to the output — it's analysis-only. In standalone mode there is no sidechain, so REF is inert.

#9. Metering panels

The footer's right side has two pills — STEREO and LUFS. They share the right column, so opening one closes the other.

#Stereo metering panel

Click STEREO to open. Three instruments, top to bottom:

#Goniometer

A 45°-rotated Lissajous of L vs R with phosphor persistence. Reads the same way as any classical vectorscope:

• A vertical line = mono content.
• A wide diamond = strong stereo content with good phase.
• A horizontal line = out-of-phase (mono-collapse will cancel).

#Correlation meter

A horizontal bar from −1 to +1. Useful at-a-glance check: stays around +0.4 to +0.9 for healthy stereo; dipping toward 0 or below 0 on a mix bus is a phase warning.

#Width per octave

10 octave bands. For each band, the bar shows the Secondary/Primary energy ratio — i.e. how wide that band is. In M/S mode this is Side/Mid; in L/R it's Right/Left. Quickly reveals which frequencies collapse to centre and which spread out.

#LUFS panel

Click LUFS to open the loudness meter. ITU-R BS.1770-4 / EBU R128 compliant. The bar runs on a mastering-range −15 to +2 LUFS scale (short-term) with the integrated value marked by an amber tick on the same axis. Five numeric readouts — Short-term, Integrated, Loudness Range, Dynamics, Avg Dynamics. Three Max-since-reset pills — Momentary Max, Short-term Max, Peak Max. Click the reset button to clear integrated + max history. K-weighting and gating run on the audio thread; the UI reads via lock-free atomics.

#10. Presets

Click the preset pill in the header to open the menu.

• Init — loads the default state (always available).
• User presets — click any saved preset to load it; the current one is checked.
• Save Preset… — prompts for a name and writes the current state (overwrites if the name exists).
• Delete — removes the active user preset (disabled on Init).
• Factory and User folders — User presets live in the OS-standard application data folder (macOS: ~/Library/Application Support/GrowlAudio/gFractor/Presets; Windows: %APPDATA%\GrowlAudio\gFractor\Presets).

A dot next to the preset name indicates the state is dirty — a parameter or a saved display setting has changed since the preset was loaded. Loading another preset, saving, or loading Init clears the dot.

#What a preset stores

A preset saves the APVTS parameters plus the display/view state — channel mode, view mode, vertical scale, time window, spectral coloring, the waterfall FFT/colour/scroll/reassign settings, and the spectrum's FFT / overlap / decay / slope / smoothing.

What a preset does not store — these are global per-user and apply across all instances: the Preferences-panel settings (trace colours, dB/Hz ranges, frequency scale, theme, UI scale, brightness, fill mode, split toggles, tooltip and band-hint toggles, reference guideline lines, curve order, analytics consent, and keyboard shortcuts), plus window size, panel divider position, and the daily update-check cache.

#11. Settings (Preferences)

Click the SETTINGS pill in the header. A modal panel overlays the view, organised into six tabs:

#Analyzer

#Traces

#Guidelines

Up to four configurable horizontal reference lines on the spectrum. Each has an enable toggle, a colour swatch, a text label, and an anchor-dB slider — handy for marking target levels.

#Display

#System

#Keys

A master Shortcuts On/Off switch (disable if the DAW eats keystrokes), plus a remappable list of every keyboard action — rebind any shortcut to a key that suits you.

Save commits all changes; Cancel discards them; Reset restores factory defaults.

Note: only gain, dryWet, bypass, outputPrimaryEnable, outputSecondaryEnable, and transientLength are exposed as DAW-automatable parameters. The Preferences settings above are user-global, not per-session — they apply across all instances of the plugin and are not stored in presets or session state.

#12. Keyboard shortcuts

Shortcuts can be globally disabled — and individually remapped — in Preferences → Keys.

#Channel

#View

#Display overlays

#Spectrum parameter cycling

#Misc

#Mouse

#13. Standalone & About

gFractor ships as a standalone app alongside the VST3 and AU plugins. The standalone window uses the native OS title bar, and audio device settings live in the Help menu (Audio Settings…).

The Help menu also opens a custom About dialog — the gFractor brand mark, a link to growl-audio.com, and credits, rendered as a native overlay that matches the rest of the interface. (There may be a little something hidden in there for the curious.)

#14. Troubleshooting

Reference mode shows nothing. The sidechain input isn't routed. See section 8 for your DAW's sidechain setup. In standalone mode there is no sidechain — REF will be inert.

Pressing Tab / R / Z etc. does nothing. Either the plugin window doesn't have keyboard focus (click anywhere inside it first), or your DAW captures the key before gFractor sees it (common with Tab in Live and Pro Tools). Workaround: change modes via the footer dropdowns, or disable/remap shortcuts in Preferences → Keys.

Tab won't switch to L+R mono mode. That's expected — Tab cycles only M/S → L/R → TRN. Select L+R from the footer Mode dropdown.

Spectrum looks coarse at the low end. Increase FFT size (key F). Below 80 Hz, frequency resolution is limited by the FFT and a smaller size won't resolve adjacent bass notes.

Spectrum is choppy. Increase Overlap (key O) and/or set Decay to Slow (key D). If CPU is the constraint, drop the FFT size.

Plugin uses high CPU. The biggest cost factors are FFT × Overlap. Try 4096 / 4× as a baseline; reserve larger sizes / 8×–16× for static-track analysis. Gradient fill and High-DPI Spectrum also cost more — switch Fill to Solid/No Fill or turn High-DPI off if needed. The oscilloscope, waterfall, and metering panels are comparatively cheap.

Preset state didn't recall correctly. Presets store APVTS parameters plus display/view state (channel mode, view, FFT/overlap/decay/slope/smoothing, waterfall settings). They do not store Preferences-panel settings (trace colours, dB/Hz ranges, frequency scale, theme, UI scale, brightness, etc.) — those are global per-user. If something didn't recall, check whether it's a Preferences setting rather than a preset value.

The Help button has a small dot on it. A newer version of gFractor is available. Click Help → Check for Updates to see the version number. The check is local and once per day — no telemetry.

Update check failed / I want to disable it. The check hits growl-audio.com/plugins/gfractor/version.json once per calendar day on a worker thread. No telemetry is sent. There is no UI toggle to disable the check itself; if you need to block it, block the domain at your firewall.

gFractor 1.2.0 — © GrowlAudio. Built with the JUCE Framework.