It can be useful to have an online tool that can convert MP4 files into different formats like AVI, WMV, MP3, OGG, FLAC and so on.
MP4 to MP3 converter is a free online tool that does just that. This tool supports a maximum file size of 100 MB for conversion.
Using it is simple :
Upload the source file to be converted through Choose File.
Next, from the drop down, choose the output format from Convert to.
Choose Advanced Settings for changing the sampling rate, audio bitrate and quality if needed.
Hit Convert Now for the process to begin. It will upload the source file and then convert it.
Once it is complete, click on Download the Converted File to use it.
All done.  This is a useful and free tool for working with small  multimedia files.
Do try it out.
Happy converting.