MP3- audio

MP4- audio and video

MP5- audio, video

In AVS Video Editor, you can extract the audio.

To change the audio in the Audio/Music track, simply delete it and put something else in its place.

To change the audio of a video in the video track, first Mute the audio of the video. Then place alternate audio in the Audio/Music track.

There is only one audio track to work with in Windows Movie Maker. The only other audio track is connected to the Video Track (the video's audio).

Therefore, you can only have one video (with audio) in the Video Track and one audio/music insertion in the Music/Audio Track.

Video is Audio's partner.