Imported from curiositech/some_claude_skills (.claude/skills/2000s-visualization-expert/SKILL.md). Install upstream with npx skills add curiositech/some_claude_skills --skill 2000s-visualization-expert. Copyright stays with the author.

2000s Music Visualization Expert

Expert in recreating the legendary 2000s music visualization era - Milkdrop, AVS, Geiss - using modern WebGL and Web Audio APIs.

When to Use

✅ Use for:

• Implementing Milkdrop-style psychedelic visualizations
• Butterchurn library integration (WebGL Milkdrop)
• Web Audio API AnalyserNode FFT/waveform extraction
• GLSL fragment shaders for audio-reactive effects
• Full-screen immersive music experiences
• Real-time beat detection and audio analysis
• Preset systems and visualization transitions

❌ NOT for:

• Simple spectrum bar charts (use Canvas 2D)
• Static audio waveform displays
• Video editing or processing
• Non-audio generative art
• Audio playback/streaming issues (use audio-engineer skills)

The Golden Era (Summary)

Milkdrop's magic: Layering simple effects - blur, zoom, rotation, color shift - with audio-reactive parameters.

→ See references/butterchurn-guide.md for full history and integration.

Core Technologies

Butterchurn (WebGL Milkdrop)

• 1.7k GitHub stars, MIT licensed
• Full preset compatibility with original Milkdrop
• npm: butterchurn, butterchurn-presets

import butterchurn from 'butterchurn';
const visualizer = butterchurn.createVisualizer(audioContext, canvas, {
  width: window.innerWidth,
  height: window.innerHeight,
  pixelRatio: window.devicePixelRatio || 1,
});
visualizer.connectAudio(audioNode);
visualizer.loadPreset(preset, 2.0);  // 2s blend

Web Audio API FFT

const analyser = audioContext.createAnalyser();
analyser.fftSize = 2048;
analyser.smoothingTimeConstant = 0.8;
const frequencyData = new Uint8Array(analyser.frequencyBinCount);
analyser.getByteFrequencyData(frequencyData);

Critical: FFT bins are linear but hearing is logarithmic! Use logarithmic mapping.

→ See references/web-audio-fft.md for frequency band extraction.

GLSL Shaders

Pass audio data as 1D texture, use uniforms for bass/mid/treble:

uniform float u_bass;
float glow = smoothstep(0.5 - u_bass * 0.3, 0.0, dist);

→ See references/glsl-shaders.md for complete patterns.

Anti-Patterns to Avoid

1. Ignoring AudioContext State

What it looks like: Visualization silently fails Why it's wrong: AudioContext starts suspended, needs user interaction Fix: Resume on click: await audioContext.resume()

2. Linear Frequency Display

What it looks like: Bass dominates, treble invisible Why it's wrong: FFT bins are linear; first 100 bins might be 0-2kHz Fix: Use logarithmic bin mapping (code in references)

3. No Smoothing

What it looks like: Jittery, seizure-inducing visuals Why it's wrong: Raw FFT data is noisy frame-to-frame Fix: analyserNode.smoothingTimeConstant = 0.7

4. requestAnimationFrame Without Cleanup

What it looks like: Memory leaks, multiple render loops Fix: Store animation ID, call cancelAnimationFrame on unmount

5. Hardcoded Canvas Size

What it looks like: Blurry on retina, wrong aspect ratio Fix: Multiply by devicePixelRatio, handle resize events

6. Blocking Main Thread

What it looks like: Choppy audio, dropped frames Why it's wrong: Heavy shader compilation on UI thread Fix: Compile shaders during loading, not during playback

Preset Recommendations

Psychedelic/Trippy:

• Flexi, martin + geiss - dedicated to the sherwin maxawow
• Rovastar - Fractopia

Smooth/Chill:

• Flexi - predator-prey-spirals
• Geiss - Cosmic Strings 2

High Energy:

• Flexi + Martin - disconnected
• shifter - tumbling cubes

Integration Checklist

• AudioContext created and resumed on user interaction
• AnalyserNode connected to audio source
• Canvas sized correctly (account for devicePixelRatio)
• Render loop with requestAnimationFrame
• Cleanup on unmount (cancelAnimationFrame)
• Preset loading with blend time
• Resize handling
• Full-screen support with ESC to exit
• Track info overlay (z-index above canvas)
• Cursor hiding after inactivity

Performance Tips

1. Lower texture ratio for older GPUs: textureRatio: 0.5
2. Reduce fftSize if not needed: 512 or 1024 vs 2048
3. Use will-change: transform on canvas
4. Avoid DOM updates during render loop
5. Profile with Chrome DevTools GPU timeline

References

→ references/butterchurn-guide.md - Complete Butterchurn integration → references/web-audio-fft.md - FFT extraction and frequency analysis → references/glsl-shaders.md - Audio-reactive shader patterns

This skill covers: Butterchurn/Milkdrop | Web Audio FFT | GLSL shaders | Full-screen visualization | Audio-reactive art