A Dock menu appears when the user Control-clicks an app’s Dock icon. This menu automatically includes system-provided menu items for initiating actions like opening the app, quitting the app, hiding the app’s windows, showing the app’s windows, revealing the app in the Finder, keeping the app in the Dock, and opening the app at login.
Music MiniPlayer includes other useful items such as the Now Playing track as well as player controls such as Play, Pause, Previous, and Next commands. This way, you never have to bring Music MiniPlayer to the foreground to be able to control it.