File Ownership

I asked Foobar this and he couldn't come up with a perfect solution so I'll toss it out to the community. I have a directory (/mp3) that all the contents of that folder should be owned by the user/group mp3. Easy enough if it's already full of a files, a big chown -R would fix it. Is there a way to specify that all files that are copied/moved/created in this directory automatically are owned by the user/group mp3?