iTunes: Just how random is random?

By David Braue on 08 March 2007

Think that song has appeared in your playlists just a few too many times? David Braue puts the randomness of Apple's song shuffling to the test -- and finds some surprising results.

Quick -- think of a number between one and 20. Now think of another one, and another, and another.

Starting to repeat yourself? No surprise: in practice, many series of random numbers are far less random than you would think.

Computers have the same problem. Although all systems are able to pick random numbers, the method they use is often tied to specific other numbers -- for example, the time -- that means you could get a very similar series of 'random' numbers in different situations.

This tendency manifests itself in many ways. For anyone who uses their iPod heavily, you've probably noticed that your supposedly random 'shuffling' iPod seems to be particularly fond of the Bee Gees, Melissa Etheridge or Pavarotti. Look at a random playlist that iTunes generates for you, and you're likely to notice several songs from one or two artists, while other artists go completely unrepresented.

This phenomenon has been observed widely across the world, with many conspiracy theorists suggesting there was more method than madness to Apple's randomisation routines.

Just what are they implying? Consider, for a minute, that you're a music industry marketer. There could be little more tempting than direct access to the ears -- and, indirectly, the wallets -- of tens of millions of iPod users around the world.

Through payment of a fee, the theory goes, a record label could increase the rotation frequency of their own music by tweaking Apple's randomisation formula. Popular songs and artists from their catalogue would pop up on playlists time and again, potentially explaining why your 50-strong playlist includes half a dozen Jackson 5 tracks but no Jackson Browne.

Less insidiously, iTunes could be tracking the songs you like the most -- it already does this -- then rotating them more often into its playlists.

Concerns over the randomness of Apple's randomness have even reached the ears of Steve Jobs, who has emphatically denied that the iPod's shuffle feature -- and the design of the iPod Shuffle itself -- is anything more than random. Just tell that to the hundreds of forum participants posters who have posted their complaints about the devices' playlist approach.

After an afternoon spent listening to far too much Bon Jovi, we decided to put iTunes to the test.

Building the perfect library
To evaluate iTunes' randomness, we borrowed a Mac Mini from Apple, with its fresh install of Mac OS X ensuring that we were working with an empty iTunes library and an otherwise completely clean slate.

We purchased AU$170 worth of Apple iTunes Music Store prepaid cards, then proceeded to go on a carefully planned shopping spree. As it was necessary to have multiple songs from one artist to observe any untoward clustering, we purchased five songs from each of four artists, with four artists chosen arbitrarily from the online artist lists of each of the major music labels (EMI, Sony, Universal and Warner Music).

This gave us a total of 80 songs. To see whether popular songs were being rotated more frequently, we also purchased 20 more songs from Billboard's current (as of late February) Top 50 chart, which represented a variety of labels. All told, we purchased and downloaded 100 iTunes songs from the iTunes Music Store (download the spreadsheet for the full song list here).

We then used the Smart Playlist feature to force iTunes to make random playlists 25 and 40 songs long, respectively. Ten playlists of each length were created, providing a total of 20 playlists and 650 possible song positions. Each song list was exported to a text file for analysis using Microsoft Excel.

If Apple and the labels were including any information to change songs' priority, it would arguably be stored in the downloaded AAC files. To test this, we also added another 100 MP3 files, previously ripped from a variety of CDs, that definitely contained no extra coding information whatsoever. These artists included Def Leppard, Bon Jovi, Erasure, Maroon 5, Bob Seger and even John Denver & The Muppets for variety.

With 200 songs in the iTunes Library, we then repeated the random playlist test, creating an additional ten playlists with each of 25 and 40 songs.

Topics: apple, itunes, ipod, shuffle, random, music, songs, playlist

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Comments (91)

  • Cassandra commented on 09/12/2009 11:30

    I have a playlist of 100 songs that I created and wanted to shuffle through. I found that iTunes on both my Mac and my iPhone were playing through the same subset of songs (approximately 20). So I unchecked all of the ones it liked to shuffle through. Now, when I start playing this playlist on shuffle, it stops after one song. This is absurd. I think it is one thing to favor songs, but not to perform at all when the favored songs are removed is ridiculous.

    I need another option.

  • Ryan commented on 29/11/2009 16:13

    The problem is how you define "random". Read more into probability theory. For example, if you have 13 randomly selected people in the room, it is more than half likely that 2 of them will share a birthday. (This seems surprising, counterintuitive even, but it is true.) Additionally, there is no "random number generator" developed, so it is obvious that the program does not generate 100% random playlists.

  • robbo commented on 14/12/2009 21:35

    kinda true but I thought it was more like 22 people in a room??

  • Tommii commented on 08/11/2009 23:04

    I had a playlist of 50 songs on shuffle, there was only one song that was in the playlist twice ans surprise-surprise apple's "shuffle" feature played them back to back.

  • Fiiish commented on 03/11/2009 11:18

    I think that the random issue is not just with itunes but with the mac book pro also. I play a game called civilization 4 on a mac book pro running Mac OSX 10.5.8. I partitioned the drive and run a copy of windows to play the game. When the game starts you can choose to play music randomly from a chosen file. I play mine from an external hard drive with a music folder. As long as the game continues the music seems random, but if you reload the game the same same band begins almost every time. For about a year every reload played Jethro Tull, and now its on a jefferson Airplane series. Not only that but if you reload again it plays a different Jefferson Airplane song in the same order on each reload. No randomness there. I have tried shuffeling the order of the songs on the hard drive with no change. If I play the game with the hard drive on any other pc the music is totally random. I even had a friend bring over his hard drive with a similar song list and the mac again went on its Jefferson Airplane kick. Any ideas on how to solve this would be great.

  • Fiiish commented on 03/11/2009 10:37

    I think that the random issue is not just with itunes but with the mac book pro also. I play a game called civilization 4 on a mac book pro running Mac OSX 10.5.8. I partitioned the drive and run a copy of windows to play the game. When the game starts you can choose to play music randomly from a chosen file. I play mine from an external hard drive with a music folder. As long as the game continues the music seems random, but if you reload the game the same same band begins almost every time. For about a year every reload played Jethro Tull, and now its on a jefferson Airplane series. Not only that but if you reload again it plays a different Jefferson Airplane song in the same order on each reload. No randomness there. I have tried shuffeling the order of the songs on the hard drive with no change. If I play the game with the hard drive on any other pc the music is totally random. I even had a friend bring over his hard drive with a similar song list and the mac again went on its Jefferson Airplane kick. Any ideas on how to solve this would be great.

  • cereal commented on 29/10/2009 01:46

    Funkleberry - thank you! Itunes definitely repeats certain songs while skipping others forever. It's particularly noticeable if your mp3's came from albums, like most of mine did. I use iTunes for "random" shuffle almost all the time, that's the main thing it has for me over actually putting on a record on the "stereo." But it clearly is not "random" or even close. I swear I hear"Hang on to Yourself" at least once every couple days, but never any other tracks from Ziggy Stardust - ever.

    I have never bought music from Apple or downloaded anything, so I doubt I'm playing many files that have been secretly programmed by Apple to repeat more as per terms of some contract with EMI or whoever. I also don't think Apple is benefitting from me hearing Aphex Twin instead of The Byrds; but perhaps iTunes has a HAL-9000 mentality, and is trying to convert me to techno. Well, it wasn't working, and now thanks to Mr. Funkleberry, I don't have to worry about it.

    Half hour into this new "playlist" and I'm hearing songs that have not been played in probably forever. Both bad and good, but at least - clearly more random.

    Hartelijke bedankt/merci mille fois/thanks ever so much!

  • Steph commented on 11/10/2009 14:59

    I've noticed this too.
    when ever i randomize my playlists the same artist are played: Taylor Swift, Cobra Starship, Flo-Rida, Kanye West and P!nk. and other artist that are famous right now.
    These artist are all in the itunes 200 right now and my itunes keeps playing their songs.
    So i believe what this article has reserched.

  • Aaron802 commented on 03/10/2009 15:11

    I did an experiment to test randomness with iTunes smart playlists. I created 26 2-second mp3 files and titled them "A", "B", "C",...,"Z" with the same genre "test1". Then I made a Helper playlist: genre="test1" select 15 items by least recently played. Then I made the Main playlist to pick from the Helper playlist and select 15 items at random. My thinking is that when a song plays on the Main playlist, it also falls off the the Helper playlist until 11 more songs have played then it makes it back on the Helper playlist. At which point, the Main playlist has a 1/15 chance of picking that song again to put back in it's lineup. What I found was no randomness at all. After letting the songs all play through, both playlists became exactly alike with the same sequence of songs. The Main playlist picked songs in the exact order they appears in the Helper playlist. Even with manual shuffling and manually playing songs out of order, both list eventually became the same. Please someone tell me my error and why this doesn't work.

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