# FFT → Audio-Reactive Visuals

**Track:** Audio-Visual & Generative Music — Advanced Creative Coding — proposed (50)
**Framework / surface:** Tone.js
**Level:** Medium
**Prerequisites:** Synthesis Fundamentals, Animation & the Frame Loop

**In one line:** Fourier analysis bins driving a p5 sketch.

## Theory, aesthetics & inspiration

The Fourier transform decomposes a signal into the sum of sinusoids that compose it, trading the time domain for the frequency domain. Its fast discrete implementation — the FFT — runs on each audio frame to yield a spectrum of magnitude bins, from sub-bass to presence, which the Web Audio API's AnalyserNode exposes directly. Mapping those bins to visual parameters — bar heights, radii, displacement, color — couples image to sound so that motion tracks the music's actual energy rather than a guessed beat. The aesthetic is synesthetic legibility: a kick swelling a form, a hi-hat glittering the edges, the eye reading what the ear hears.