iPod Modify ID3 tags for mac?

[almostvindiesel]

Hi all--

I'm looking for a (preferably freeware) mac program that allows me to modify ID3 tags based on a file name (not the other way around).

FILE NAME * * * * * * * * * * * *
"The Strokes - Reptilla"

to

ID3 TAG * * * * * * * * * * * *
Artist: The Strokes
Song: Reptilla

Thanks!

~John