The update fixes issues with the equalizer and performance when switching views in large libraries.
iTunes 11.1.3 is a free download through the software update mechanism of the Mac App Store.iTunes 11.1.3
This version of iTunes resolves an issue where the equalizer may not work as expected and improves performance when switching views in large iTunes libraries. This update also includes additional minor bug fixes.
Note: If you are using OS X Mavericks, your book library can now be found in iBooks for Mac.
For information on the security content of this update, please visit: support.apple.com/kb/HT1222.
Article Link: Apple Releases iTunes 11.1.3 With Equalizer and Performance Improvements.