MP3Gainについて語らないか Part 2

こんな感じでどうか

setlocal
set MP3GAIN="C:\Program Files\MP3Gain\mp3gain.exe"

for /R %1 %%i in (*.mp3) do call :tunes "%%i"
goto :end

:tunes
set TUNES=%TUNES% %1
goto :eof

:end
echo %MP3GAIN% /a /c /p %TUNES%

endlocal
pause
exit