When I play one song, many songs are entered into "Next Up".

Whenever you start a song playing in iTunes it will normally queue up all the checked songs in the current view that follow. E.g. if you have an album showing, then the rest of the album, a playlist, the rest of the playlist, etc. If shuffle play is enabled then the whole of the view can play, less any tracks marked as skip when shuffling and unchecked tracks as before. Grouping is a field that can be edited using the Song Info dialog and displayed as a column in the songs view. When you shuffle by groupings and there are two or more songs with the same value in this field then when they get selected they should all play together in sequence. Likewise shuffling albums should result in whole albums playing, again with the caveats for skip when shuffling and unchecked tracks.

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Lyrics are not generally provided, though some may be available if you are an Apple Music subscriber.

Unchecking all songs will mean that any song you play will play through just once and stop regardless of your repeat and shuffle settings. Unless you want this behaviour all the time it may be best to leave them checked and use the column browser, playlists, or the search box with Search Entire Library unticked to narrow down the view to what you want to listen to. Unchecked songs are normally excluded from syncing. You can quickly check or uncheck all songs in the current view by ctrl-clicking a checkbox.

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