grep - match anything but given filetype

I want to clean out my music library so I don't get any more "search for suitable plugin" messages from Rhythmbox when it sutubles across some WMA-Relic.

I have the tools, but now I want to FIND these files. I can get a list of all music files with ls, then pipe this to grep and catch all the mp3s like this:

ls */* | grep \.mp3$

Now I want to filter OUT all the MP3s, how would I do that? I messed around a lot with ^ and ~ and ! but I never seemed to get anywhere. I KNOW for a fact there are a few WMAs in there, but why should I search manually when I have a computer xD

Can anyone help?

grep -v will return all lines that don't match your search query

you can also use:

find . ! -name "*.mp3"

to do the whole thing in one command.

Have a look at the -v switch to grep, which inverts matching.