In addition to static playlist support, version 3 of iTunes introduced support for smart playlists. Smart playlists are playlists that can be set to automatically filter the library based on a customized list of selection criteria, much like a database query. Multiple criteria can be entered to manage the smart playlist.
Any user of iTunes can publish a playlist to the iTunes Store with his or her own preferences, which is called an iMix.
Introduced in iTunes 4.5, the "Party Shuffle" playlist was intended as a simple DJing aid. By default, it selects tracks randomly from other playlists or the library, but users can override the automatic selections by deleting tracks (iTunes will choose new ones to replace them) or by adding their own via drag-and-drop or contextual menu. This allows a mixture of both preselected and random tracks in the same meta-playlist. The playlist from which Party Shuffle drew could be changed on the fly by the computer user, but doing so will cause all randomly chosen tracks to disappear and be replaced.
Party Shuffle was renamed iTunes DJ in iTunes 8. When iTunes was updated to 8.1 quite a few features were added to iTunes DJ. The free Apple Remote application for the iPhone and iPod Touch was also update at this time that added a new iTunes DJ option in the settings screen when the user is connected to a Wi-Fi network and a new song request feature is enabled in iTunes DJ on the hosts. Along with the song request feature voting on songs in the queue was added, the more votes a song gets the high in the queue it will be and sooner it will be played. Song voting can only be done when song requesting is enabled and in two ways: the first by right clicking on a song in the iTunes DJ queue on the hosts computer in iTunes, the second is in the Remote application ether connected with the iTunes DJ option by a guest or by the host in the full playlist section. When song requesting is enabled a customizable welcome message is displayed below the host's shared library name in the button used to connect to iTunes DJ.
Playlists can be played randomly or sequentially. The randomness of the shuffle algorithm can be biased for or against playing multiple tracks from the same album or artists in sequence (a feature introduced in iTunes 5.0, and later discontinued in iTunes 8.0). iTunes DJ can also be biased towards selecting tracks with a higher star rating.
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