From Audacity Manual

Audacity projects contain audio clips arranged onto tracks along with additional information. These projects are stored in AUP files. Whilst this Audacity Project Format makes working with the audio easier and more rapid, the format is not compatible with any other audio program. When you Save an Audacity project, you save in the Audacity Project Format, i.e. as an AUP file. The AUP file cannot be used in an MP3 player.

To use the audio outside Audacity, you Export the audio into another format, as described on the File Menu. The format you need will depend on how you plan to use the audio. For an MP3 player you will want MP3 format. For burning to a CD you will want WAV format.

If instead you have audio which you want to use in Audacity but which wasn't recorded in Audacity, you will usually need to Import the audio. This is also an option on the File Menu.

Dependencies

When you open or import an uncompressed audio file such as WAV or AIFF, Audacity saves time by not making a copy of the file. Instead, it refers back to the original file as you manipulate it within your project (while not ever making any changes to that file unless you tell it to). You must be careful not to modify files that you have open in Audacity with another program. When you save an Audacity project, Audacity will tell you about these dependencies and give you the option of copying all of the audio data into your Audacity project, making it safe to delete, move, or modify the original audio files if you choose. At any time, choose Check Dependencies... from the File Menu to see if your project depends on any external files.

Outline

Suggested tutorial (walk through):

• Open a new project.
• Generate some sound using DTMF.
• Close Audacity saving the project.
• Try to play the AUP in Media player. You can't.

• Open the project you just had.
• Export the audio as WAV.
• Close Audacity.
• Play the WAV in Windows Media Player. You can.

Much less top heavy with explanation, much more a walk through of steps. Doesn't try to tackle 'dependencies'.

Possible title for tutorial:

• "Understanding Project File Format"

• Or rather than a new tutorial, add the information in in the relevant place in Tutorial_-_Editing_an_Existing_File? It already has a note that it needs the exporting/saving difference explaining.

Old Text (to be Cannibalized)

Audacity projects are stored in an AUP file, which is a format that has been highly optimized for Audacity so that it can open and save projects extremely quickly. In order to achieve this speed, Audacity breaks larger audio files into several smaller pieces and stores these pieces in a directory with a similar name as the project. For example, if you name a project "chanson", then Audacity will create a project file called chanson.aup which stores the general information about your project, and it will store your audio in several files inside a directory called chanson_data. The Audacity Project format is not compatible with any other audio programs, so when you are finished working on a project and you want to be able to edit the audio in another program, select Export As... from the File Menu.

Audacity is sometimes used to open a file, make a quick change, and write it back to disk, and it is sometimes used to mix together a dozen tracks with hundreds of effects to create a song. For all of these needs, big and small, Audacity encapsulates whatever you're working on inside an Audacity project.

In Audacity, each window represents an Audacity project. A project represents one complete piece of audio, which might be a short recording, a 3-minute song, or an hour-long entire CD. It can have multiple tracks, hundreds of audio clips, labels, and more, but a single timeline. Audacity projects can be saved to disk and then loaded back later so you can continue where you left off. When you save an Audacity project, nearly everything about the window is saved: all of your tracks and editing information, for example. The only thing that is lost when you save and close the window is the history; you can no longer undo changes. (However, you can always save "snapshots" of your project at any time.)

Saving vs. Exporting

Audacity projects are saved to disk in a way that is very efficient for Audacity. While the format is open in theory, it is not intended to be used by other programs. When you want to create audio that can be opened by another program, copied to an iPod, or burned to a CD, for example, you should export the file as a standard format like WAV or MP3. See Audio File Formats for more info. However, when you export audio, you lose information about separate tracks, labels, and other Audacity-specific editing information. Only the final mixed audio is saved. So you should save an Audacity Project if you want to make changes later.

Audacity Projects on disk =

Rather than using a single file, an Audacity project is split into several files, often hundreds or thousands, each one containing about 10 seconds of audio. When you save a project called MyRecording, for example, Audacity creates two items on disk:

• MyRecording.aup - the main project file
• MyRecording_data - a folder containing the small audio files making up the project

Both of these items, and all of the files inside the data folder, are totally critical to the project! If you move one to another location, you must move the other. If you need to send an Audacity project to someone else, and a standard format like WAV or MP3 won't do, it's often best to create a Zip archive of the project file and data folder.

If you accidentally lose the project file or some of the data files, you will need to have Audacity recover as much of the project as possible. You will lose a lot of editing information, but often much of your recording can be salvaged. See Recovery for more information.

In most software programs you talk about Opening and Saving. Audacity can do those too. So what's up with Importing and Exporting?

A really common operation in Audacity is to combine many audio files into one. This could be for creating a mix tape, splicing together different segments from a mix tape, or reassembling a complete symphony from movements stored as four different CD tracks.

While it is possible to open each file and then copy and paste the contents into the same file, the preferred method in Audacity is to open just one project window, then import all of the different audio files into that window.

When the Import dialog is open, shift-click, control-click, or cmd-click (Mac) to select multiple files to import at once.

You can also drag and drop files directly into Audacity's window.

Save: saves a project, in Audacity's internal format. Fast to open again later, but you can't use the Audacity project in a different program.

Export: mixes all of your audio down to a single mono or stereo track. You lose any extra information, like multiple tracks, volume edits, or labels; only the audio is saved.

Export formats

In the chapter on Digital Audio, we talked a little bit about compression. When you export audio from Audacity, you have to decide whether to export it compressed or uncompressed.

The most common uncompressed export formats are WAV (most common on Windows), AIFF (most common on Mac). Good for CD-quality audio. Good for burning onto a CD. Not good for emailing or uploading to the Internet unless it's just a few seconds worth of audio.

Audacity supports three common types of compressed audio as well: MP3, MP2, and Ogg Vorbis.

MP3 is the most common file format found on the Internet. If you're creating a song or podcast to share with others online, this is probably your best bet. If you use the 128 kbit compression setting, you're getting a factor of 10 compression.

MP2 is used in radio broadcast industry. If you're sending something to a radio station, this may be the format they expect. For anything else, there's probably no good reason to use it, because MP3 supercedes it.

Ogg Vorbis is a free alternative to MP3. Independent listening tests consistently show that an Ogg Vorbis file that's the same size as an MP3 file will sound better, or equivalently, if you have two files that sound the same, the Ogg Vorbis file will be smaller. You can find free Ogg Vorbis players for Windows, Mac OS X and Linux, and hundreds of portable digital players support it as well. However, Ogg Vorbis is still less well-known, and many portable devices like the iPod do not support it. The fact that Ogg Vorbis is great and patent-free means that Audacity comes with full Ogg Vorbis support built-in, while MP3 support must be added on separately.