Mike Dominy: ‘Taking music from a CD and putting it on your computer is called ‘ripping,’ not burning. ‘Burning’ is what you do when you transfer that music back to a CD. Otherwise, you provided a very good explanation of how iTunes discovers what CD you’re listening to. The only problem is you’re probably going to receive a ton of emails from other folks about this process. Your article leads one to believe that Apple came up with this scheme when they actually used the database that was already out there in Internetland.’

James Redekop: ‘The system for determining a CD’s identity based on the number and lengths of its tracks is not an Apple invention. It was developed a while ago by a bunch of hobbyists in a project called CDDB [CD database]. They distributed a program which could create an (almost) unique id number for a CD and call out to a server on the Internet to get the information. The programmers didn’t have a big database of CDs, though; they just had their own personal collections. But the program was so useful that, when other people started using it, they would enter their own collections into the CDDB system as well (I contributed a few dozen myself), and the library grew. CD-playing software such as WinAMP and MusicMatch started incorporating CDDB clients, and the whole thing took off pretty quickly. CDDB was eventually bought out by a private business (http://www.gracenote.com/), much to the consternation of everyone who contributed, who all of a sudden saw all the work they did become a profitable piece of intellectual property for someone else. Apple most likely licenses Gracenote’s CDDB database for its iTunes lookups.’

Peter Cioe: ‘There are two CDDB services: Gracenote, a for-profit company, and FreeDB a open source service.’

Mike Mangino: ‘The CD lookup functionality of iTunes has been around quite a while. Take a look at http://www.musicbrainz.org/history.html for a reasonable history.’

Jonathan Hochman: ‘What iTunes does, in looking at the disk to see how many ‘cuts’ it has and how long each one is, is called hashing. A hash table uses a seemingly random characteristic of the data, the more scattershot the better, to create a fast index. It is widely used. Meanwhile, if you haven’t already, please treat yourself to reading Godel, Escher, Bach by Hofstadter.’

☞ As one Amazon reviewer put it in awarding five stars:

The greatest book ever written by a human being.
April 25, 1999 Reviewer: Eliezer Yudkowsky from Atlanta

As pure Art, as magnificent intelligence incarnated as absolute beauty, this is the greatest book ever written by human hands. It is a terrible thing to contemplate that 150,000 people die every day without having read this book. Don’t let it happen to you.

And speaking of books:

Doug Jones: ‘Thanks for suggesting Lies and the Lying Liars…. I did a lot of driving for the holiday and listened to the book on tape version. It was definitely worth listening to. Now I’m gonna break down and buy myself a copy of the book.’

Janet: ‘I bought and read the book. THANK YOU. I have purchased several more copies for holiday gifts and expect to purchase many more for anytime gifts. FINALLY, someone has articulated intelligently what I have been screaming all along.’

☞ If you want to listen to it on your iPod, via Audible.com [full disclosure: I own Apple LEAPs and Audible.com stock, and I want everyone in the world to read Lies and the Lying Liars Who Tell Them] click here.


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