Audio Reactivity

Hydra can make visuals that react to sound in real time through FFT analysis.

The a object: audio analysis

Property/Method	Description
a.fft[n]	The value of a frequency band (0-1)
a.show()	Show the FFT visualization
a.hide()	Hide the visualization
a.setBins(n)	Set the number of frequency bands
a.setSmooth(n)	Set the smoothing (0-1)
a.setScale(n)	Set the sensitivity
a.setCutoff(n)	Set the noise threshold

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A basic example

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Different frequencies, different parameters

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Modulating with loudness

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A pulsing kaleidoscope

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Reactive noise

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Feedback with audio

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Strudel patterns in Hydra

The H() function lets you use Strudel patterns as Hydra inputs:

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feedStrudel: visualizing the pattern

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Audio reactivity tips

Good settings

a.setBins(4)       // Enough for bass/mid/high
a.setSmooth(0.8)   // Smooth transitions
a.setScale(8)      // Good sensitivity
a.setCutoff(0.1)   // Cut off the noise

Frequency bands

Index	Frequencies	Use
a.fft[0]	Lows (bass)	Pulsing, scale
a.fft[1]	Low mids	Rotation
a.fft[2]	High mids	Color, brightness
a.fft[3]	Highs	Fine details

Avoid chaos

// Bad: too much reactivity
osc(() => a.fft[0] * 100).out()

// Better: moderate values with a base
osc(() => a.fft[0] * 30 + 10).out()