A quick way to turn an MP4 video into an audio file is to use an online conversion tool. Below we’ve described how to convert files using the free online converter at videoconverter.com.
Go to the Online Video Converter website
To upload the video you want to convert, click Add Your Media, select the desired video, and hit Open. Then you need to change the output format. To do this, click the list of formats (the default format is MP4), select Audio, and pick MP3. Click Convert; when the video is converted, you will be able to download the MP3 file to your computer.
This online service is a great choice if you have one relatively small file to convert. Note that the file size is limited, and you can’t convert more than one file at a time.