@echo off & setlocal
SET pathToFFmpeg="C:\_DOWNLOADS_\ffmpeg-20150710-git-033dc39-win64-static\bin\ffmpeg.exe"
echo %*
pause
:process
set d=%~a1
set d=%d:~0,1%
echo "%~1"
if %d% equ d (
    :: process as a directory/folder feed, not a file-name-set
    echo "%~1" is a directory...
    pause
    pushd "%~1"
    for %%a in (*.*) do (
        echo processing %1\file: -------- "%%~a"
        if not exist "%%~dpna.mp3" %pathToFFmpeg% "%%~dpnxa">"%%~dpna.mp3"
        pause
    )
    popd
) else (
    :: here processes a single file
    echo file-name process: "%~1"
    pause
    if not exist "%~dpn1.mp3" %pathToFFmpeg% "%~dpnx1"
    pause
)
shift
if [%1] neq [] goto :process
pause