How to add an audio background into a video from a MP4 video source ?

1. Upload any video (WebM, MKV, MP4 format) from your device. If the video is short tick the loop attribute of the control video.

2. Click once on upper right corner of the canvas. This trick will hide the MP4 video.

3. Upload the MP4 video audio source

4. Your video will start automatically to record with the audio track from the second MP4 video.

5. Let the audio play until the end and Download your video

Here is video result with audio track from a second MP4 video made in few clicks with 011.video web app :