Here's how you can see a popup in the Dock when iTunes starts playing a new song. 1. Open a terminal window. 2. Type in the following command, then hit Enter. defaults write com.apple.dock notification-always-show-image -bool TRUE; killall Dock 3. You can deactivate it using these commands: defaults delete com.apple.dock itunes-notifications defaults delete com.apple.dock notification-always-show-image;killall Dock
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See the iTunes Track in the Dock | Amsys