w00ties

If you're comfortable opening your computer's command prompt, FFMPEG is a great free app for this. It's a sort of Swiss Army Knife for media files. It can save the audio out of a video, raise/lower the volume, trim, fade, etc. All without burning some kind of watermark into the new file or pestering you to buy a paid version of the app (there is none). An example of a command to save the audio out of a video would be something like FFMPEG -i yourmoviefile.mp4 -c:a copy -vn audioclip.mp4 -c:a copy tells FFMPEG to copy the audio as-is, and -vn tells it to omit the video. You could further