Here's a shorter version, without the /while loop since $findfile has it's internal loop

Code:
 alias RenameMP3 { noop $findfile($iif($1-,$1-,$sdir(c:,Select MP3 Directory)) ,*.mp3,0,.rename $qt($1-) $qt($replace($1-,_,$chr(32)))) } }


Syntax: /renamemp3 ["c:\file\path"]

* file path is optional. A select dir dialog will pop-up if no path is entered.

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