Apple has updated iTunes to version 12.1.
You can download the app via the App Store or directly here.
The update introduces a new iTunes widget for Notification Center in OS X Yosemite. The update is supposed to allow you to see what is playing, skip ahead, and buy songs while listening to iTunes Radio directly from Notification Center when the notification appears.
To modify settings, go to System Preferences > Notifications or click on the gear icon at the bottom of Notifications next to the Spotlight icon and adjust the settings to your liking.
The update also improves performance when syncing with your iPhone, iPad or iPod touch.