merge two audio tracks into one track

I was able to do this by using Web Audio API. I fetched the audio tracks from both the streams and joined them into one using audio context.

var OutgoingAudioMediaStream = new MediaStream();
OutgoingAudioMediaStream.addTrack(OutgoingStream.getAudioTracks()[0]);

var IncomingAudioMediaStream = new MediaStream();
IncomingAudioMediaStream.addTrack(IncomingStream.getAudioTracks()[0]);

const audioContext = new AudioContext();

audioIn_01 = audioContext.createMediaStreamSource(OutgoingAudioMediaStream);
audioIn_02 = audioContext.createMediaStreamSource(IncomingAudioMediaStream);

dest = audioContext.createMediaStreamDestination();

audioIn_01.connect(dest);
audioIn_02.connect(dest);

var FinalStream = dest.stream;

This worked perfectly.