gl-spectrogram 
Render spectrogram in webgl or 2d.
Usage
var createSpectrogram = require('gl-spectrogram');
//lightweight 2d-canvas version
//var createSpectrogram = require('gl-spectrogram/2d');
var spectrogram = createSpectrogram({
//placement settings
container: document.body,
canvas: canvas,
context: 'webgl',
//audio settings
maxDecibels: -30,
minDecibels: -100,
maxFrequency: 20000,
minFrequency: 20,
sampleRate: 44100,
weighting: 'itu',
//grid settings
grid: true,
axes: false,
logarithmic: true,
//rendering settings
smoothing: 0.5,
fill: 'inferno',
background: null,
//useful only for webgl renderer, defines the size of data texture
size: [1024, 1024]
});
//push frequencies data, view is shifted for 1 slice
spectrogram.push(data);
//for even timeflow push data in setTimeout, stream data event, scriptProcessorCallback etc.
setTimeout(() => {
spectrogram.push(getData(data));
}, 100);
//set data colormap or background
spectrogram.setFill(colormap|color|pixels);
spectrogram.setBackground(color|array);
//update colors, grid view
spectrogram.update(opts);
//called when freqs being pushed
spectrogram.on('push', magnitudes => {});
spectrogram.on('update', magnitudes => {});
//latest frequencies data in db
spectrogram.magnitudes;
spectrogram.peak;