If you want to convert MP4 to MP3 for free, Freemake Video Converter will help you to do it quickly and easily. Download the freeware here and follow the instructions below to convert MP4 to MP3 just in three steps.
Use "+Video" button or drag-n-drop feature to add all the MP4 videos you want to convert to MP3.
Click "to MP3". Choose a ready preset or create a custom one. Select "Export to iTunes" if you want to transfer MP3s to your iPod, iPad or iPhone.
Convert MP4 to MP3
Click "Convert" to start the conversion process. Extract audio from other videos in the same way. Alternatively, you can download MP3 free from YouTube.