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Do most music CDs have 12 tracks?

This might sound like some wild conspiracy theory, but I'm looking at my music collection and it sure seems like most of them have exactly 12 tracks, no more, no less. Is there some marketing reason this would be the case, or am I witness to some great conspiracy? :-)

Dave's Answer:

Don't panic! There's no magic to it. A music CD can hold 60-70 minutes of music and the average pop song is about 5 minutes long. Do the math and you'll see that gives you about 12 songs per CD.

But I figured I'd do a bit of math here too. I have about 425 CDs in my music library, a wide range of genres, from country to classical, jazz to blues, and here's what I found:

428 albums analyzed
5369 tracks examined

The results:

Occurrances	Number of Tracks
65	10
56	12
50	11
41	9
25	8
24	15
22	14
17	13
17	7
15	18
15	16
14	1
11	20
9	19
8	6
7	17

That is, 65 of the 428 albums have 10 tracks, 56 have 12 tracks, 50 have 11 tracks, 41 have 9 tracks, and so on. Percentage-wise, this means that less than 15% of my 428 tested CDs have exactly 12 tracks, but averaging everything out, yes, the average music CD has 12.54 tracks.

So there's your answer. No conspiracy theory involved! :-)

How I did these calculations

For those of you who would like to analyze your own iTunes library, here's how I did these calculations. I popped open a Terminal window on my Mac, moved into my "iTunes Music" folder within my "Music" folder, and...

$ find . -type d -mindepth 2 -print | wc -l
428

The predicate "-type d" is directories, so that tells me the number of Cds, and

$ find . -type f -mindepth 2 -print | wc -l
5369

That's the number of individual tracks across all those CDs. This means, by the way, that the average CD in my library, at least, has 12.54 tracks. So maybe there is some sort of conspiracy!

To figure out how many tracks there are per CD is a bit more tricky. To accomplish this, I actually wrote a short shell script:

#!/bin/sh

cd "/Users/taylor/Music/iTunes/iTunes Music"

for directory in $( find . -type d -mindepth 2 -print | sed 's/ /_-_/g' )
do
dirname="$(echo $directory | sed 's/_-_/ /g')"
echo $( ls "$dirname" | wc -l ) tracks: $dirname
# ls "$dirname" | wc -l
done

exit 0

When run it lists tracks and albums:

$ tracks-per-song.sh | head
14 tracks: ./10,000 Maniacs/MTV Unplugged
12 tracks: ./10cc/Greatest Hits 1972-78
10 tracks: ./Acoustic Alchemy/Blue Chip
9 tracks: ./Acoustic Alchemy/Red Dust & Spanish Lace
9 tracks: ./Acoustic Alchemy/Reference Point
12 tracks: ./Adrian Legg/Mrs. Crowe's Blue Waltz
6 tracks: ./Al Di Meola/Elegant Gypsy
9 tracks: ./Al Di Meola, Paco de Lucia & John McLaughlin/The Guitar Trio
11 tracks: ./Al DiMeola/Splendido Hotel
11 tracks: ./Al Jarreau/All I Got

When I comment out the echo line and just output the number of tracks as a number with the wc command, I can easily slip the script into a typical collation sequence:

$ tracks-per-song.sh | sort | uniq -c | sort -rn
65 10
56 12
50 11
41 9
25 8
24 15
etc etc etc

Classic Unix command line stuff! :-)

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Categorized: Shell Script Programming , Unix and Linux Help , d) None of the Above (Article 6682)
Tagged: apple itunes, music cds, shell script programming
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