Add user-defined fade-in and fade-out to all input files using SoX.

SoX_fades_ask.cmd

@echo off
set /p fadein="Fade-in length (in seconds): "
set /p fadeout="Fade-out length (in seconds): "
for %%A in (%*) do sox %%A "%%~nA"_faded%%~xA fade t %fadein% 0 %fadeout%