Can't Convert a Video MP4 file to Audio

[potchboy]

I have a music video on my PC which I am trying to convert to Audio MP3 with VLC but it does not seem to work.
Is it perhaps that there are six tracks on the recording and if so is there a way of converting all 6 tracks in one Convert/Save?
O/S Win 7 64 bit
Most grateful if someone can help me here please.
potchboy