A lightweight JavaScript library which handles all the audio processing for a web music visualiser.

It's called bars.js as the library converts audio into its frequency spectrum representation: This frequency spectrum representation is sampled at even intervals, which is displayed as bars in many music visualisers.

The MusicVisualiser object has a property called bars - this is an array of bar heights, which is the primary data source for creating a music visualisation.

Full documentation of the library can be found on the wiki of this GitHub repository.

It includes the following sections:

• Best Practice
• Control How the Audio is Processed
• Getting Data from the Music Visualiser
• Letting the User Upload Their Own Sound File
• Pause and Play the Audio
• Setting the Audio Element, File Input Element and Audio URL

HTML

<audio controls id="audioElementId"></audio>

JavaScript

let mV = new MusicVisualiser();

mV.audioPlayer = "audioElementId"; // Specifying where the audio is coming from.
mV.soundFileURL = "music.ogg";
mV.numberOfBars = 128;

function playSoundFile() {
  mV.playSoundFileFromURL();
}

// Any function that is called every frame.
function animate() { 
  mV.updateVisualiser(); // Updates the contents of the bars array.
  
  for (let i = 0; i < mV.bars.length; i++) {
    drawBar(i, mV.bars[i], mV.bars.length); // The bars are drawn to the screen.           
  }
}

A live demo with interactive code can be found on CodePen.