How do I avoid duplicates when adding MP3 folders

The typical cause of duplicates is adding content from a folder stored outside of the iTunes Media folder while iTunes is set up to copy new additions into it. Once iTunes creates an internal copy it has no reference to the path outside the media folder, so if you add that folder again it will see every file as new.

Place any content that you want to add to iTunes inside the iTunes Media folder and it will add it once, even if you add the folder to the library over and over again. If you let iTunes "Keep the iTunes Media folder organized" it will rearrange content as you add it to the library and edit tag data. There is even a dedicated folder for the task called Automatically Add to iTunes so you don't even need to make use of File > Add Folder to Library. If you really prefer to organize your media manually (and I urge you not to because it is a lot of effort for no real gain) if you use the basic iTunes Media folder layout as a starting point, and keep all of the media inside the iTunes Media folder, then it will be much easier to backup your library and move it to a new drive or computer when the time comes.

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The default path for the iTunes library folder is C:\Users\<User>\Music\iTunes.

The default path for the media folder is C:\Users\<User>\Music\iTunes\iTunes Media.

Both can be edited; the media folder via Edit > Preferences > Advanced, and the main library path by holding down shift as you start iTunes and using the choose or create library option.

Ideally you want the iTunes Media folder inside the iTunes folder as this puts the library in the portable shape that is easy to move between drives, migrate between computers, and backup.

You can use Edit > Preferences > Advanced > Reset to reset the media folder to the default path inside the library folder, or click the change button if required.

When you change the media folder iTunes should offer to consolidate the library. This makes iTunes make a new copy of any track currently located outside of the media folder inside the media folder and connects the database to that new copy. Once complete it is up to the user to do the house keeping of cleaning up the originals. Alternatively I have another script called ConsolidateByMoving whose purpose should be obvious.

There is another option that controls the internal structure of the library. With new libraries it should be set correctly, but a library that has been migrated from iTunes 8 or earlier might still be in the old shape. If you go to File > Library > Organize Library and find the "Rearrange files..." option is not greyed out then you should tick this and click OK.

See also Grouping tracks into albums.

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