half the time when i when i import an album into my iTunes library it will rename some of the songs the way i want it to eg: "01 song name" but some it will keep the original file name eg: : "01_artistname_albumname_songname"
it will copy all the songs into the correct folders in my iTunes library though
anyone have any idea why itunes does this?
its a real pain having the check the folder and manually rename each song and then redirect itunes to the renamed song every time i import an album, especially when i import a bunch at a time.
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Let's start with this:

Are your tags correctly filled out and do you have 'Keep iTunes Music folder organized' in the Advanced tab of your preferences?
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keep music organized has always been ticked
and if you mean tags as in the names of the songs that come up in itunes then yes.
everything is absolutly correct within itunes, but when i look at the songs within the actual folders, they are all messed up.
its something itunes has always done.
does it have anything to do with large itunes librarys? mine is currently 135gig
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iTunes can not read the information from the file names. It gets it from something called ID3 tags which are a data section inside the MP3 file. It is the info inside those tags that iTunes uses to organize your songs into folders AND rename them. When you rip the songs with iTunes, it automatically fills in those tags. When you get the songs from unknown sources they can be messed up, empty, unstandardized or non existent.

Before importing songs into iTunes it is good practice to clean up the tags. You can do this with specialized software: tag editors. They offer many tools to fill them in, including the possibility to get the info from the file name itself and place them in the ID3 tag. The most common tag editors are: Tag&Rename, ID3-TagIt and mp3tag.
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The size of the library shouldn't be a problem, some have libraries much lager than that, mine is about the same, never a hickup.

Just a hunch; are these mp3 files or another format? Wav? Aiff?
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they are uaually mp3's
if the file names were messed up before i import them, why would they only ever properly tag half the songs
it has to be some fault with itunes specific to my instalation i think
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If you change the artist or album name, do they still stay together in the new folder but with some songs still misnamed? What if you fake-edit the song name? Anything happens then?
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I just noticed this when I added some mp3s to my library last night. I always fix tags (using Tag&Rename) before importing the files. Most of the tracks were renamed when they were imported, but a few of them retained the original filenames. As soon as I made a small change to the tags using iTunes, the files were then renamed.
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