After hearing one artist played over and over during a shuffled play
of your entire music library in iTunes you may think your player has a
preference of its own. Apple claims the iTunes' shuffle algorithm is
completely random.
1
The shuffle algorithm chooses songs "without replacement." In other
words, much like going through a shuffled deck of cards, you will hear
each song only once until you have heard them all... or until you have
stopped the player or selected a different playlist.
iTunes Party Shuffle
2
is a different matter. Its algorithm selects songs "with replacement,"
meaning the entire deck of cards is reshuffled after each song is
played. The
play higher rated songs more often option does exactly what it says, but how much preference is given to higher rated songs?
To test the option's preference for 5-stars, I created a short
playlist of six songs: one from each different star rating and a song
left un-rated. The songs were from the same genre and artist and were
changed to be only one second in duration. After resetting the play
count to zero, I hit play and left my desk for the weekend. To satisfy a
little more curiosity, I ran the same songs once more on a different
weekend without selecting the option to
play higher rated songs more often. Monday morning the play counts were as shown in Table 1.