# run auto-import in background
When checked, MC will automatically detect any changes to files/folders in the 'watched folders' list and update the library/import new files automatically. If unchecked, this will not happen, nor will any of the other task options, unless you click on "Tools > Run Auto Import Now"
# analyze audio
When checked, MC will analyze audio files and store BPM, intensity, peak level and replay gain values in the library.
# Build Thumbnails
MC builds thumbnails on the fly as you view files. If this option is checked, MC will build thumbnails for the entire library in the background, which initially, can be a big job, but also a one time only job. This should speed up view building and switching as the thumbnails will not need to be built on the fly.
# Get Cover Art
There have been many changes to the coverart system in recent builds, but my understanding is that it won't fetch cover art if a file already has art associated.
# Update for external changes
If you close MC, then open a different application and make some tag changes to files in MCs watched folder list, then start MC, MC will detect those tag changes and update the library accordingly.
# Fix broken links
If you use explorer to delete a file that is in your MC library, MC will detect that, and remove the 'broken link' from the library.
If the links are broken because a network or removable drive happens to be offline when MC is running, MC will remove the items from the library, unless you choose the option to 'protect network files'
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It's very important to understand that these options are not restricted to only the folders in your watched folders list. These are library maintainence tasks that are applied across the entire library.
You mention that the analyze audio option is always on regardless. This should not be the case and could be a bug. I've turned mine off atm as it's causing a crash everytime it runs and I've not got round to trouble shooting it yet. This will be investigated now that it's been highlighted.
-marko.