Load locally saved files to tonejs

Question

I am trying to create an app with the electron-react boilerplate where i can create audio files.

I found Tone.js, which allows me to play sounds but loading the sample files seems close to impossible. Is there a way to give the audio data to Tone?

I am using Sampler but i dont know how to create the URLs to transmit the data

Answer 1

Looking at the implementation of Player.load it can handle ArrayBuffers and luckily, using an <input type="file"> can be used to get an ArrayBuffer with a FileReader

Here is some sample code that assumes that there's a file input with id "local-file" in your HTML and you have Tone.js loaded at this point:

document.querySelector('#local-file').addEventListener('change', async function() {
  await Tone.start();
  // create a FileReader to process the chosen file
  const fileReader = new FileReader();
  // when it's read into an ArrayBuffer, we can access that in the result property of the event target
  fileReader.onload = async (event) => {
    // create a Tone.js Player connected to the audio output
    const player = new Tone.Player().toDestination();
    // create a ToneAudioBuffer from the ArrayBuffer with file contents. event.target.result is the ArrayBuffer with the file content
    const buffer = await player.context.decodeAudioData(event.target.result); 
    // add the buffer to our player    
    player.buffer = buffer;
    // once we're ready, start the player.
    Tone.loaded().then(() => {
      player.start();
    });
  }
  // read the selected file into an ArrayBuffer
  fileReader.readAsArrayBuffer(this.files[0]);  
});

Answer 2

I ended up using a mix of the above answer and what i saw in the documentation:

let fileDataA4 = fs.readFileSync('path/to/A4.mp3');

// create a Tone.js Player connected to the audio output
const player = new Tone.Player().toDestination();

let arrayBufferA4 = await new Blob([fileDataA4]).arrayBuffer();

// create a ToneAudioBuffer from the ArrayBuffer with loaded buffer
const bufferA4 = await player.context.decodeAudioData(arrayBufferA4);
                

let fileDataA5 = fs.readFileSync("path/to/A5.mp3");

let arrayBufferA5 = await new Blob([fileDataA5]).arrayBuffer();

const bufferA5 = await player.context.decodeAudioData(arrayBufferA5);
                
let sampler = new Tone.Sampler({
        urls: {
            "A4" : bufferA4,
            "A5" : bufferA5
        }
}).toDestination();
                
Tone.loaded().then(() => {
    sampler.triggerAttackRelease("C4", "1n")
})

This way, you only need to load 2 mp3 files, the sampler does the rest for you