iTunes Match is SWEEEEET! However, if you have a large music library you may find that it takes a long, long time to perform the iCloud matching. You can help cut down this time and save a lot of aggravation by doing some preliminary work. (MUST HAVE NEWEST ITUNES.)
BE CAREFUL! Be very, very careful. Make a backup before proceeding!
Keep in mind that you may need to quit and start iTunes several times during the
1. EMPTY TRASH. This is important for the next step.
2. DELETE DUPLICATES and MOVE TO TRASH. However, be warned that the iTunes duplicate finder only matches song titles. You will need to examine whether the song is indeed a duplicate or that the title is included in more than one album, or that the durations are different (short version versus long version). If you have a huge number of duplicates, you may want to find an alternative, third-party, duplicate finder where you can specify rules as to what deems a true duplicate. Try going to MacUpdate.com or CNET Downloads to find such and application, or use the App Store (Lion and Snow Leopard)
3. CREATE JUNK MUSIC FOLDER: On your Desktop create a folder that you will place deleted music into as a safety net.
4. MOVE TRASHED MUSIC TO JUNK MUSIC FOLDER: Just in case something goes wrong, you have saved the music you trashed. Repeat this procedure any time you have trashed any music.
5. DELETE MUSIC YOU NO LONGER WANT. You can also move it to the junk music folder after trashing.
6. RENAME TRACKS WITH NO NAMES!!!! You can do this manually or use iTunes’ Advanced menu to choose Get Track Names. You can do multiple tracks at a time. Works best when doing albums. The manual method takes longer, but you get to listen to the music before naming.
7. RUN ITUNES MATCH. This may take all day, all night, all the next day or longer depending on how many tracks need to be evaluated, how much music needs to be uploaded and the speed your Internet upload connection. Wait for MATCH to be completely done before moving to STEP 7.
8. BE CAREUL HERE!!! DELETE LOW BIT RATE (less than 96kbps) AND MP3 (if you prefer AAC) FILES THAT HAVE BEEN MATCHED. This will allow the next step to go smoothly. Only delete music that has been matched!!!! When deleting, you will be given the option to delete from iCloud. DO NOT DELETE FROM ICLOUD!!! Delete only from your library! Note: if you have low bit rate music that cannot be matched, iTunes will NOT upload it to iCloud! You will need to manually raise the bit rate, somehow.
9. DOWNLOAD FROM ICLOUD. Select all the music that has an icon of a tiny cloud with a down arrow. Right-click (control-click) and select Download from iCloud. This will replace all your low-bit rate and MP3 music (which you deleted) with MP4-AAC (advanced audio codec) high bit rate (256kbps) music. You will want to be on a FAST CONNECTION!
10. EXAMINE YOUR ITUNES LIBRARY. Make sure everything you wanted done has been done. If you are missing music, move that music and ONLY THAT MUSIC from the Junck Music folder you created.
11. CHECK FOR MATCH DUPLICATES: It appears that iTunes Match has a better duplicate finder than iTunes itself. iTunes Match appears to indicate as dulplicated songs in your library that have the same title AND album name. You may NOT want to delete these duplicates until all other steps are complete; perhaps after a week!
12. BACK UP YOUR LIBRARY: Clone, use Time Machine, or somehow otherwise back up your iTunes folder that contains the Library and ALL your music.
13. MOVE JUNK MUSIC FOLDER TO TRASH
14. EMPTY TRASH. This will open up drive space.
15. REMEMBER. Itunes Match, uploading and downloading can take hours if not days (for very large libraries) and will test your patience.
FOR MORE INFORMATION, go to Apple’s support website to read all their Knowledge-base articles about iTunes Match
OR
follow this link to a great Macworld article:
http://www.macworld.com/article/163658/2011/11/itunes_match_what_you_need_to_know.html