Filter to Exclude Filenames

In a folder, I have MP3 files which look like the following:

MyFile.orig.MP3
MyFile.MP3
MyFile2.orig.MP3
MyFile2.MP3
etc.

I want to see all the MP3 files except files with ".orig." in the filename.

What filter expression would work?

Thanks in advance.

NOT %_filename% HAS ".orig"

Yes - that works.

Thank you!

I am happy to have found this.
I need to persistently omit the Mac sidecar files (when viewing on the PC), which start with a dot and underscore, i.e. "._filename.ext".
Can it be implemented ON start of the app?

You could apply a filter like:
NOT %_filename% MATCHES "^\..*"

Understood. But where can I setup that filter so it runs by default with the start of the program?

enter it and don't remove it.
MP3tag remembers the currently set filter between sessions.