Audio node
Audio Spectrum
Renders a real-time frequency spectrum from Audio FFT data — bars / line / filled styles, log/linear/mel scales, dB or linear power, grid and labels. Includes an interactive selection region: drag to select a frequency band and output its energy as a control signal.
Inputs
| Port | Type | Default |
|---|---|---|
| EnableHides the plot without stopping the analysis behind it. | bool | true |
| FFT DataThe analysed audio to draw. Cable it from Audio FFT; nothing renders until this is connected. | structure | — |
| XHorizontal centre of the plot in Grafit units, with 0 in the middle of the view. Any value works; far enough out it simply leaves the frame. | float | 0 |
| YVertical centre of the plot in Grafit units, 0 being the middle of the view. | float | 0 |
| WidthPlot width in Grafit units. 2 spans the short edge of the view; larger values run wider than the frame. | float | 2.0 |
| HeightPlot height in Grafit units, measured from the bottom to the top of the drawn area. | float | 0.4 |
| Min FreqLowest frequency shown, at the left edge, in Hz. If it reaches or passes Max Freq it is pushed back just below it. | float | 20 |
| Max FreqHighest frequency shown, at the right edge, in Hz. Zero or less falls back to 20000. | float | 1000 |
| Power MaxFixes the top of the level axis. 0 auto-scales to the loudest recent peak; any positive value freezes the scale so levels stay comparable over time. | float | 0 |
| Show GridDraws the frequency and level grid behind the spectrum. | bool | true |
| Show LabelDraws the Hz and level numbers. Turning it off also frees the side margins they reserved, so the spectrum fills the full width. | bool | true |
| Label SizeText size of the axis numbers, in screen points. Held at 1 or above. | float | 12.0 |
| Line ThicknessStroke width for the line and filled styles, in screen points. Held at 0.1 or above. | float | 1.0 |
| ColorBase colour of the spectrum. The colour mode in Settings can override it with a frequency or amplitude tint. | color | — |
| InteractiveLets you drag and resize the selection frame straight in the render view with the mouse. | bool | true |
| Sel XHorizontal centre of the selection frame along the frequency axis. Clamped to 0…1, where 0 is Min Freq and 1 is Max Freq. | float | 0.5 |
| Sel YVertical centre of the selection frame on the level axis. Clamped to 0…1, 0 being the bottom of the plot. | float | 0.5 |
| Sel WidthWidth of the selection frame as a fraction of the frequency axis. Clamped to 0…1. | float | 0.3 |
| Sel HeightHeight of the selection frame as a fraction of the level axis. Clamped to 0…1. | float | 0.5 |
| ThresholdHow full the selection must be before Trigger fires. Clamped to 0…1; the live amount comes out of Fill. | float | 0.5 |
| Freq StepSpacing, in Hz, of the Frequencies table resampled from the spectrum. Held at 0.1 or above, and the table caps at 2048 entries so tiny steps widen automatically. | float | 50 |
| Trigger HoldKeeps Trigger on for this many milliseconds after the last crossing, so brief dips do not make it flicker. Negative values behave as 0. | float | 100 |
Outputs
| Port | Type |
|---|---|
| Image | image |
| WidthPlot width in Grafit units. 2 spans the short edge of the view; larger values run wider than the frame. | float |
| HeightPlot height in Grafit units, measured from the bottom to the top of the drawn area. | float |
| Peak Freq | float |
| Peak Power | float |
| Fill | float |
| Trigger | bool |
| Selection | structure |
| Frequencies | structure |
What It Does
Audio Spectrum draws the FFT as a live frequency display — the classic "dancing bars" — right in your output. Beyond looking great, it has a trick: you can drag a selection box over a range of frequencies and turn just that band into a control signal.
How It Works
Connect Audio FFT's FFT Data. Choose a render style (bars / line / filled) and how frequency is spaced — logarithmic (musical, matches how we hear), linear, or mel. Limit the displayed range with Min/Max Freq, toggle a grid and labels, and pick a color. The interactive selection: when enabled, drag a rectangle on the display; the node outputs that band's energy as Selection and fires a Trigger when it crosses a threshold.
Parameters
| Parameter | What it does |
|---|---|
| Min / Max Freq | The frequency range to display. |
| X / Y / Width / Height | Position and size on screen. |
| Color | Bar/line color. |
| Interactive | Enable drag-to-select a frequency region. |
| Threshold | Level at which the selected band fires its Trigger. |
Outputs: Image (the visual), Peak Freq, Peak Power, Trigger, and Selection (the chosen band's energy).
Examples
- On-screen analyzer — a beautiful spectrum overlay for a music visual.
- Snare trigger — drag-select the snare's frequency range and use Trigger to flash a light only on snares.
- Custom band control — select a vocal range and drive an effect from its energy.
Tips
- Use the logarithmic scale for music — it spreads the bass out the way your ears do.
- The selection region is the easiest way to react to one specific instrument instead of the whole mix.
Open Audio Spectrum in the interactive catalog →
Audio Spectrum is one of 381 nodes in Grafit Pro.
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