Audio files come in a number of different formats. Some are lossy, such as AAC and MP3; they save space compared to the original files, but some of the original data is lost during compression. Some formats are lossless, such as Apple Lossless, FLAC, and SHN; although these files are 40 to 60 per cent the size of uncompressed audio, they can be converted back to their original form without the loss of a single bit. Finally, some formats are uncompressed, such as WAV and AIFF; they represent the exact data from a CD or a master.

If you’ve bought music from the iTunes Store, you’ll have AAC files at 256kbps – that’s kilobits per second, an indication of the quality of the compression; higher numbers are better. (Really old iTunes Store files are 128kbps, and protected by conversion-unfriendly DRM, or digital rights management.) If you’ve purchased music from Amazon, you’ll have MP3 files, most likely encoded using VBR (variable bit rate) compression, so the bit rate you see will be an average.

Files from other sites may be in FLAC or even WAV format; the former is the most common for lossless files, notably from sites that sell live or classical music. There may come a time when you’ll want to convert some of your audio files to another format. Depending on your originals, and the reason for the conversion, there are several ways you can do so.

Use iTunes to convert your audio files

Even though this window says Import Settings, it’s actually where you choose the settings to convert files

One reason to convert files to another format, or even another bit rate, is to save space. For example, you can have iTunes convert music files to 128kbps AAC format when syncing to an iOS device if you wish. This often makes sense if your device has limited storage and/or you listen to your music outdoors or on the go, where a difference in quality (say from 256kbps to 128kbps) won’t be very noticeable. Just check the Convert Higher Bit Rate Songs To 128kbps AAC option on iTunes’ Summary screen for your device when it’s connected to iTunes, and the process will happen automatically when you sync. (Note that such a conversion can take a long time if you have a lot of files to convert.)

iTunes supports AAC, Apple Lossless, MP3, AIFF, and WAV files. You can convert to or from any of these formats as needed. But you can use iTunes to convert in other ways as well. Say you have some AAC files you bought from the iTunes Store (DRM-free, as all recent iTunes music comes) and you want to play them on a device that supports only MP3 files; iTunes can do this for you.

First, find the files you want to convert, and add them to a new playlist. Open iTunes’ Preferences, click on the General icon, and then click on the Import Settings button near the bottom of the window. This shows your current CD-ripping settings (which also apply to conversions made with iTunes). You can then make changes to these settings. If you want to convert your files to MP3 format, for example, choose MP3 Encoder from the Import Using menu and then choose a bit rate from the Setting menu.

You should never choose a bit rate higher than that of your original files – your music won’t sound any better. But you can choose the same bit rate, so if you have 256kbps AAC files from the iTunes Store, choose Custom from the Setting pop-up menu, and then set the Stereo Bit Rate pop-up entry to 256kbps to make sure you don’t lose any quality. (Converting from one lossy format to another will result in a very slight loss of quality, but in reality it probably won’t be noticeable to most people.) Click OK as necessary to save your settings and to close the Preferences window.

Back in your playlist, select all the tracks, and then choose Advanced > Create MP3 Version. (If you’ve chosen a different format,
its name will appear instead of MP3.) iTunes will convert your files, and you can search for them in your library when it has finished.
(Hint: sort you music library by clicking Date Added, and those files will float right to the top.)

Use another app to convert your audio files

There are a large number of audio file formats out there, many of which iTunes doesn’t support – notably FLAC, Shorten (SHN), and Ogg Vorbis. So what can you do if you have files in one of these formats and you want to add them to iTunes? Luckily, there are a number of programs that can convert audio files from one format to another.

The free X Lossless Decoder (XLD) from a company called tmkk (macworld.com/7290) is our tool of choice, because it manages every audio file format we’ve ever come across, along with some we’ve never heard of. It even supports cue files (text files that describe how tracks on CDs are separated). Stephen F Booth’s free Max (www.sbooth.org/Max) is another tool that converts many audio file formats. And if you have Roxio’s £84.99 Toast 11 Titanium (www.roxio.co.uk) – and even some earlier versions – you can convert from FLAC or Ogg Vorbis to iTunes-friendly formats as well.

With all three of these programs, conversion involves choosing an output format and a bit rate, and dragging the files you want to convert onto the program’s window or icon. (With Toast, click on the Convert tab, and then choose Audio Files from the pop-up menu near the top of the window.)

If, for example, you’ve bought some music in FLAC format and want to listen to the files in iTunes – a concert from Nugs.net’s Livedownloads site (www.livedownloads.com), for example – use XLD or one of the other programs to convert the files to Apple Lossless; since both formats are lossless, you’ll have exactly the same data in the resulting files. (Converting from one lossless format to another does not result in any change in quality.) And you’ll retain any metadata in the original files as well.

Once you’ve decided on the format you want to use, the bit rate, and other settings, converting music files is a drag-and-drop (and wait) operation. With these tools, you’ll be able to convert any audio files into the format you need.   MW