The createMediaStreamTrackSource() method of the AudioContext interface creates and returns a MediaStreamTrackAudioSourceNode which represents an audio source whose data comes from the specified MediaStreamTrack.

This differs from createMediaStreamSource(), which creates a MediaStreamAudioSourceNode whose audio comes from the audio track in a specified MediaStream whose id is first, lexicographically (alphabetically).

track

The MediaStreamTrack to use as the source of all audio data for the new node.

A MediaStreamTrackAudioSourceNode object which acts as a source for audio data found in the specified audio track.

In this example, getUserMedia() is used to request access to the user's microphone. Once that access is attained, an audio context is established and a MediaStreamTrackAudioSourceNode is created using createMediaStreamTrackSource(), taking its audio from the first audio track in the stream returned by getUserMedia().

Then a BiquadFilterNode is created using createBiquadFilter(), and it's configured as desired to perform a lowshelf filter on the audio coming from the source. The output from the microphone is then routed into the new biquad filter, and the filter's output is in turn routed to the audio context's destination.

navigator.mediaDevices
  .getUserMedia({ audio: true, video: false })
  .then((stream) => {
    audio.srcObject = stream;
    audio.onloadedmetadata = (e) => {
      audio.play();
      audio.muted = true;
    };

    const audioCtx = new AudioContext();
    const audioTracks = stream.getAudioTracks();
    const source = audioCtx.createMediaStreamTrackSource(audioTracks[0]);

    const biquadFilter = audioCtx.createBiquadFilter();
    biquadFilter.type = "lowshelf";
    biquadFilter.frequency.value = 3000;
    biquadFilter.gain.value = 20;

    source.connect(biquadFilter);
    biquadFilter.connect(audioCtx.destination);
  })
  .catch((err) => {
    // Handle getUserMedia() error
  });

• Web Audio API
• Using the Web Audio API
• MediaStreamTrackAudioSourceNode