I’m on a roll with iTunes-related tips lately. To better myself and others, I have made scripts that can edit music file tags, create technical playlists not possible even with Smart Playlists, and other workarounds for missing features and requests. Some work out-of-the-box, and the rest just need you to enter your desired customizations in the javascript code. These free scripts work on Windows only, but Mac users can use Applescripts. I’m no whiz at programming, but I managed to come up with some rudimentary plugins that achieve crucial functions that should be helpful for many people on many occasions (like processing in batches). This saves time and makes things more convenient.

Has Lyrics
All songs that have lyrics (anything but blank) in the lyrics ID3 tags are put in a playlist.
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Adjust Play Count
Change the “Played Count” number of selected songs that you can set to whatever number you want.
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Undo Play Count
If a song played that you didn’t really listen to, or you just want to subtract the number of plays of selected tracks, use this. This does not edit the time stamp listed as “Last Played,” but it will undo the number of play counts. This might come in handy if you are using a auto-rating plugin or other play dependent software that works with iTunes. This would come in handy if you fall asleep with music and still want to keep track of how many actual listens you have made (like in a smart playlist).
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Relative Batch Rating
This script is set to add an extra star to selected songs. Depending on how you set it up, it will shift all the ratings by whatever amount of stars you want. Adjust Ratings at increments of 20 (20=1 star, 40=2*, 60=3*, etc). You can even do half-stars by making half-rating quantities (10, 30, 50, 70, and 90). A good tip is if you want to add just a half a star, change the 20 in the text file to 10 and choose the track and execute.
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Lyrics Search
This one takes pretty long to search through the lyrics of selected songs. Find a word, string, or more than one input at a time. Matches go into a playlist. I searched the word love after highlighting 600+ songs and it took at least five minutes to complete. Otherwise, extremely useful.
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Append To Comment
With tracks that are highlighted (selected), it adds user-defined text to a comment without erasing and overwriting previous comment text. It will not add the same text that is already in the comment field (so if you have “live” already written in the comments and are adding “live” with this script it will only have one occurrence of the word).
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Append To Grouping Field
Same as above, except it attaches text to the end of Grouping tags without destroying the current data.
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Before you can use the javascript, you need to rename the *.txt file to *.js then double-click to run them. Be sure to read the top of the script for special instructions before renaming and executing the plugin.

If you want me to configure any plugins so all you have to do is double click (no editing the code), I may create a custom script or help troubleshoot and give you support, especially if you send a tip via PayPal.

Otto also has other javascripts that actually helped me make my own. I had to search for official iTunes class namings to figure out how to control iTunes specifically, but glancing over his code was enough to guide me to create these.

Changelog:
2007.06.30 – Added an undo script for playcount, basically an offshoot of my “Adjust Play Count” script except it changes relative to the current number.
2007.07.26 – Made a rating script that changes relative to the existing number of “My Rating” and also can handle half-star.