How can i overlay audio with video?

So i wanted to overlay 2 files so they played together using html video controls , this is because the file it too large to fit in one whole bit . I wanted to add two videos , one with audio but a black screen and one with video but no audio and overlay.

I tried

<!DOCTYPE html>
<html>
<body>

<h1>The video element</h1>

<video width="320" height="240" controls>
  <source src="movie.mp4" type="video/mp4">
  <source src="movie.ogg" type="video/ogg">
  Your browser does not support the video tag.
</video>

</body>
</html>

but it doesn’t actually play them together on further testing.

does anyone know how i could link them together so that when it pause both of the files pause, unpause and can be skipped to a certain timestamp. I am unsure if this is accomplish and if it is possible using java-script, can you please show me how!