How to use the AudioMixer to mix the microphone and a audio file uploaded by the user?

I am using lib-jitsi-meet js, I take the file and I mix it with the local track.
I have the audiomixer but is not clear to me how I can remove the microphone audio track and put the mixed one

        var objectURL = window.URL.createObjectURL(document.getElementById("audio-mp3").files[0]);
        var audio = new Audio(objectURL);
        var stream = audio.captureStream();

          var audio_mixer = JitsiMeetJS.createAudioMixer();
          return audio_mixer

Hello tritone11, do you solve this situation? I’m doing something similar to share a browser tab with audio. After JitsiMeetJs.createAudioMIxer() is used, i add the audio streams and finally the method start(), the code says is the way to mix the streams (lib-jitsi-meet/AudioMixer.js at master · jitsi/lib-jitsi-meet · GitHub) after that i don’t know how to continue. addTrack or replaceTrack is not working, What about you?