iTunes: Just how random is random?

Say You, Say What?
Using Excel, we collated the results and counted the number of times that each song and artist appeared in the playlists iTunes had generated.

All things being equal (and random), one would expect that a field of 1300 song slots would provide enough opportunities for each of the 56 artists to be equally represented. However, this was not the case. In fact, even though each specifically chosen artist had five songs in the library, there was a large discrepancy between the most popular and least popular artists.

	Click for larger image

Lionel Richie (Universal) proved to be iTunes' most popular artist, appearing 59 times all told, for an average of 1.475 times per possible playlist (or TPP, an objective measure reflecting the fact that iTunes-purchased songs were available to iTunes during creation of 40 playlists while CD-ripped songs could only have appeared on 20 playlists).

Red Hot Chili Peppers and The Veronicas tied for second place (55 times/1.375 TPP) with Keane and Robbie Williams (53/1.325 TPP), Eskimo Joe (52/1.3 TPP), Good Charlotte (51/1.275 TPP) and Grinspoon (50/1.25) all appearing at least 50 times in our playlists. Looking further down the list, however, a curious trend appeared. Artists whose five songs were bought from iTunes were consistently more likely to appear on the random playlists than those whose songs were ripped from CD. Each of the top 15 artists, by number of songs played and songs per playlist, was bought from iTunes; those ripped from CD were far less likely to rate.

Songs by Def Leppard, the most frequently-played artist from CD, were chosen 24 times in 20 possible playlists for a TPP of 1.2--but the rate of selection for other CD artists quickly dropped off: Bon Jovi (21/2 TPP), Creed (20/1 TPP), and Gloria Estefan (18/0.9 TPP) were all slightly ahead of Andrew Lloyd Webber, the Bee Gees, Dido, Erasure, Jackson Browne, Maroon 5 and Mötley Crüe, all of which were played 17 times for a TPP of 0.85.

The least frequently played artists were all those whose songs were taken from CD, with the bottom of the rung inhabited by Kate Bush (12/0.6 TPP), Anderson Bruford Wakeman Howe (11/0.55 TPP), and Christina Aguilera and Oasis (10/0.5 TPP).

When the artists with just one song were factored in, things got even more interesting. Smack That--a current hit by Akon and Eminem--was played 17 times, which was the mean for the artists with five songs in the iTunes Library. Its TPP was 0.425, a frequency that translates to 2.125 if treated as though there were five copies of the song (we'll call that ratio TPP5). In other words, we were 1.44 times as likely to hear Smack That than any song by Lionel Richie, even though Lionel Richie had five songs in the iTunes Library.

Also played proportionally more frequently than five-song artists were Gwen Stefani's The Sweet Escape and Hinder's Lips Of An Angel (14/1.75 TPP5), Justin Timberlake's What Goes Around/Comes Around (13/1.625 TPP5), and Daughtry's It's Not Over (12/1.5 TPP5). Beyoncé's Irreplaceable, Fall Out Boy's This Ain't A Scene, It's An Arms Race, Gym Class Heroes' Cupid's Chokehold, Nelly Furtado's Say It Right (11/1.375 TPP5) all had as many playlist appearances as songs from the Red Hot Chili Peppers and The Veronicas--even though the latter artists should presumably have been five times more common.