Match chars at end of filename, but not extension

I have a list of file names like this:
Song title (30).mp3
Another song title [02].MP3
A final song (57).wma

What I would like to do is remove those track numbers. The regex I have so far, while not quite working correctly, will match " (57).wma" and replace it with nothing. Instead, I want to preserve the file extension.



Is there a way to specify for the $ anchor to start looking x characters from the end, so it won't match the file extension?

Thanks
-Z.

Try this: