I am using MM4. I initially analyzed my entire library of about 2,300 songs. Now i have only been doing one album at a time. It completes analysis and adds the track and album volume levels for that album. It then tags the files, but gets stuck on 1 file to be tagged. The next time I open MM, usually the first track is missing volume levels. All the files are either m4a or mp3. I'm not sure about the rights to modify. I shouldn't have any trouble modifying m4a and mp3 files should I? Thanks.