Firstly, if the music is mixed with the dialog, you will not be able to remove it completely, if at all. If the music has no voiceover, you can use the "F7" key which will make a blue "fade" line appear on the track. By dragging this line down, you can fade to zero. You can left click on the line to insert cue points and the fade line will only work between these points.
When the voice and music are combined, you will have to use the "remove vocals" effect in Goldwave, but do not expect miracles!!