Samsung Galaxy S III User Manual page 234

Playing Music
From the main Play Music page, tap a song in your library to
listen to it.
The Now playing screen opens and the song you touched or the
first song in the album or playlist starts to play. The tracks in
the current list play in order until you reach the end of the list
(unless you choose a repeat option). Otherwise, playback stops
only if you stop it, even when you switch applications.
Note: If you navigate away from the Now playing screen in the Music
application, the Now Playing bar appears at the bottom of the
screen.
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