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Touring iTunes

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Audio File Formats You Might Encounter When You Use iTunes

As you work with digital music and other audio files, you’ll encounter a number of file formats you need to understand. This is important because each of these formats offers specific benefits and limitations that impact what you do with your music. For example, some file formats offer better music quality versus file size than others. You definitely don’t need to have all the specifications for each of these formats committed to memory (nor will you find them in this book); instead, all you need is to be able to distinguish between them and to be able to choose the format that is the most appropriate for what you are trying to do.

Most audio file formats are encoded. This means specific compression algorithms (because this is a computer book, I am required by contract to use that word at least once) are used to reduce the size of the audio file without—hopefully anyway—lowering the quality of the resulting sound very much. The higher the compression that is used, the lower the quality of the resulting music when it is played back. Note that the words higher and lower are relative. Often, it takes a musical expert to tell the difference between encoded and unencoded music, but even if it is imperceptible to us mere mortals, it does exist.

When it comes to digital audio files, one trade-off always has to be made. And that is file size versus sound quality. When you add thousands of songs to your iTunes Library, you can easily consume gigabytes of disk space. Although you might have a humungous hard drive in your computer, you might also have other files you want to store on it, such as photos, Word documents, and so on. Even I realize that computers can be used for more than just music.

To keep the amount of disk space required to store your music to a minimum, you must encode it. When you do, you choose the settings you want to use to encode that music. The more encoding you apply, the less space the music will consume, but the lower quality the playback will be. You will quickly find a happy medium between file size and how the music sounds to you.

You’ll learn about encoding music in more detail later in the book, but for now, you should read the following sections so you can become comfortable with the various audio file formats you will encounter.

CD Audio

The CD Audio format was the world’s first widely used entry in the digital audio format life cycle. The creation of this format was the start of the CD revolution. Instead of vinyl albums, which were a pain to deal with and included lots of hisses, pops, and other distractions when played, listeners began enjoying digital music. In addition to being easier to handle than LPs, CDs provided a much better listening experience and were—and are—much more durable than records. They also sounded much better than cassettes and could be just as portable.

Eventually, CD Audio made its way to computers, which now can provide all the music-listening enjoyment of a home stereo plus much more, thanks to applications such as iTunes.

Although you can use iTunes to listen to your audio CDs, typically you will just convert those CDs into one of the newer digital formats and store that content on your computer’s hard disk so you don’t have to bother with a CD when you want to listen to music. You will also use this format when you put your iTunes music on your own audio CD so you can play your iTunes music when you are away from your computer.


Even if this book is your first foray into the wonderful world of digital music, you have no doubt heard of MP3. This audio file format started, literally, an explosion in music technology that is still reverberating and expanding today.

MP3 is the acronym for the audio compression scheme called Moving Picture Experts Group (MPEG) audio layer 3. The revolutionary aspect of the MP3 encoding scheme was that music data could be stored in files that are only about 1/12 the size of unencoded digital music without a noticeable degradation in the quality of the music. A typical music CD consumes about 650MB of storage space, but the same music encoded in the MP3 format shrinks down to about 55MB. Put another way, a single 3.5-minute song shrinks from 35MB on audio CD down to a paltry 3MB or so in MP3 format. The small size of MP3 files opened up a world of possibilities.

For example, MP3 enabled a new class of portable music devices. Because MP3 files can be stored in small amounts of memory, devices with no moving parts can store and play a fair amount of music; these were the early MP3 players, such as the Rio. Then came other devices containing small hard drives—can you say iPod?—that can store huge amounts of music, enabling you to take your entire music collection with you wherever you go. These devices are extremely small and lightweight, and their contents can be easily managed.

You will encounter many MP3 files on the Internet, and with iTunes, you can convert your audio CDs into the MP3 format so that you can store them in iTunes and put them on an iPod.


The successor to MP3 is called Advanced Audio Coding (AAC). This format is part of the larger MPEG-4 specification. Its basic purpose is the same as the MP3 format: to deliver excellent sound quality while keeping file sizes small. However, the AAC format is a newer and better format in that it can be used to produce files that have better quality than MP3 at even smaller file sizes.

Also, as with MP3, you can easily convert audio CD files into the AAC format to store them on a computer and add them to an iPod. What’s more, you can convert AAC files into the Audio CD or MP3 format when you want to put them on a CD to play on something other than your computer, such as a car stereo.

The AAC format also enables content producers to add some copy-protection schemes to their music. Typically, these schemes won’t have any impact on you (unless of course, you are trying to do something you shouldn’t).

One of the most important aspects of the AAC format is that all the music in the iTunes Music Store is stored in it; when you purchase music from the store, it is added to your computer in this format.


The Windows Waveform (WAV) audio format is a standard on Windows computers. It has been widely used for various kinds of audio, but because it does not offer the "quality versus file size" benefits of the MP3 or AAC formats, it is mostly used for sound effects or clips people have recorded from various sources. Millions of WAV files are available on the Internet that you can play and download.

You can load WAV files into iTunes, and you can even use iTunes to convert files into the WAV format. However, because MP3 and AAC are much newer and better file formats, you aren’t likely to want to do this very often. Occasionally, you might want to add WAV files to your iTunes music collection; this can be easily done, as you will learn later in this book.


The Audio Interchange File Format (AIFF) provides relatively high-quality sound, but its file sizes are larger than MP3 or AAC. As you can probably guess from its name, this format was originally used to exchange audio among various platforms.

As with the WAV format, because the MP3 and AAC formats provide a better sound quality versus file size trade-off, you aren’t likely to use the AIFF format. The most typical situation in which you might want to use it is when you want to move some music or sound from your iTunes collection into a different application that does not support the MP3 or AAC format.

Apple Lossless

The Apple Lossless format is the only encoding option supported by iTunes that doesn’t sport a fancy acronym. The goal of this format is maximum sound quality. As a result, files in this format will be larger than in AAC or MP3. However, Apple Lossless files will be slightly smaller than AIFF or WAV files.

The Apple Lossless format provides very high-quality music but also larger files sizes. If you have a sophisticated ear, high-quality sound systems, and discriminating taste in music (whatever that means), you might find this format to be the best for you. However, because storing music in this format requires a lot more space on your computer and on an iPod, you will probably use the AAC or MP3 format more.

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