MP4 files represents video files.
If you have a video file with .mp4 extension and you want to make it MP3 audio file to listen music, follow these steps.
Download MP4 to MP3 Converter from this page (is free).
Install application and start it. From the interface select the MP4 file that you want to convert it to MP3.
We have now the file on interface and we will convert it. Pay attention where your file will be saved (you can set a default Output Folder where MP3 generated files will be saved).
Select other options if you need and click Convert.
You will have very fast an MP3 file and you can play it or listen woth Winamp or other favorite audio player, or even transfer it on your mobile device to listen from there.