Audio node
Audio Analysis
Extracts low / mid / high band energy from FFT data with beat detection, BPM estimation, onset, spectral centroid and optional beat prediction — turn music into triggers and control signals.
Inputs
| Port | Type | Default |
|---|---|---|
| FFT DataThe spectrum to analyse — cable an Audio FFT's output here. | structure | — |
| Low MinBottom of the Low band in Hz (default 50). | float | 50 |
| Low MaxTop of the Low band in Hz (default 200) — kick and bass. | float | 200 |
| Mid MinBottom of the Mid band in Hz (default 200). | float | 200 |
| Mid MaxTop of the Mid band in Hz (default 2000) — snare, vocals. | float | 2000 |
| High MinBottom of the High band in Hz (default 2000). | float | 2000 |
| High MaxTop of the High band in Hz (default 12000) — hi-hats, air. | float | 12000 |
| SmoothingHow much the band levels are smoothed over time, 0 = raw every frame, 1 = very slow. Default 0.5. | float | 0.5 |
| Beat SensitivityHow easily an onset counts as a beat, 0…1. Higher fires on smaller hits; lower waits for clear ones. Default 0.75. | float | 0.75 |
| Beat Hold msHow long Beat stays true after a hit, in milliseconds (default 100). Also the shortest gap between two beats. | float | 100 |
| Beat BandWhich bands drive the beat. Low Only — kick and bass (default, ignores hi-hats). Low + Mid — kick and snare. All Bands — the full spectrum. | int | 0 |
| Max BPMAn upper limit for the tempo estimate; 0 = no limit. Set it near the music's tempo to stop double-time readings. | float | 0 |
| PredictHow far Predicted Beat runs ahead of the measured beat, 0…1 of a beat period. Default 0.5. | float | 0.5 |
| Predict Offset msA fixed shift of Predicted Beat in milliseconds, positive later, negative earlier — to line lights up with what you hear. | float | 0 |
| GainA multiplier on the incoming spectrum before analysis (default 1). Auto Gain overrides it. | float | 1.0 |
| Auto GainTracks the level automatically so quiet and loud passages both drive the bands; Gain Value reports what it chose. | bool | false |
| Tonal SensitivityHow readily Tonal Onset fires on a new note. 0.5 = measured free of false notes on deep vibrato; higher catches more legato notes but starts reading wide vibrato, choirs and chorus as new notes; lower only clear note changes. 0–1. | float | 0.5 |
Outputs
| Port | Type |
|---|---|
| Low | float |
| Mid | float |
| High | float |
| Total | float |
| Beat | bool |
| Predicted Beat | bool |
| Onset | float |
| BPM | float |
| Dominant Freq | float |
| Centroid | float |
| Gain Value | float |
| Tonal Onset | bool |
What It Does
The FFT gives you a wall of frequency bins — useful, but a lot. Audio Analysis boils it down to the few numbers you actually want for reactive visuals: how much bass, mid and treble there is right now, and when a beat hits.
How It Works
Connect Audio FFT's FFT Data. The node sums the energy in three frequency ranges (split by Low/High Cutoff) into Low / Mid / High values. Separately it watches a chosen band for sudden jumps in energy — an onset — and reports a Beat pulse, tracks the BPM, and can even output a Predicted Beat a hair early to compensate for visual latency. Auto Gain keeps the response consistent whether the music is quiet or loud.
Parameters
| Parameter | What it does |
|---|---|
| Low / High Cutoff | Where bass ends and treble begins (the band boundaries). |
| Beat Sensitivity | How easily a beat triggers. Higher = more beats. |
| Beat Band | Which band to detect beats in (usually the bass/kick). |
| Auto Gain | Automatically normalize levels across loud/quiet material. |
| Smoothing | Ease the band values for less flicker. |
Outputs: Low, Mid, High, Beat (bool), BPM, Onset, Dominant Freq, Centroid (brightness), and more.
Examples
- Kick-driven pulse — wire Beat into a trigger that flashes the background or bursts particles.
- Three-band visual — Low → a shape's size, Mid → its rotation, High → its color brightness.
- BPM-synced motion — feed BPM into an animation's speed so it stays locked to the music.
Tips
- Set Beat Band to the bass for punchy kick-detection on most music.
- If beats are missed, raise Beat Sensitivity; if it triggers constantly, lower it.
- Turn on Auto Gain for installations where the volume isn't predictable.
Open Audio Analysis in the interactive catalog →
Audio Analysis is one of 381 nodes in Grafit Pro.
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