Managing Audacity Projects

From Audacity Manual

Audacity saves your audio as a project while you are working on it. It is important to note that a project is not a single audio file but is a complex set of files managed by Audacity.

Audacity projects have a top-level AUP file and a related folder containing the sound files (the audio data). The AUP is not a sound file, it is merely a list of instructions that tell Audacity how to construct the project from the sound files in the folder. Audacity projects can only be used by Audacity.
To make an audio file (such as WAV or MP3) for playing on your music player, or for use in other programs, use one of the Export audio commands.

Structure of an Audacity project

The Audacity Project Format stores all Audacity tracks and clips, labels, amplitude envelope points, gain and pan data, together with other project data. The audio can be a recording, imported files, generated audio or a mixture of any of those. Projects are a convenient way to save your extended multi-track piece and come back to it later exactly as you left off.

The structure of a saved Audacity project is:

An AUP project file - the name of the project followed by ".aup", for example "my_song.aup"
A _data folder with the same project name and in the same folder as the .aup file, for example "my_song_data"
Within that _data folder, a sub-folder structure with lots of little AU files which are individual segments of the audio data.

Note that default behavior on Windows and Mac is to hide certain file extensions ; if this applies, the .aup file will only appear as "my_song" in the computer. On Windows, the .aup extension will be hidden if Audacity was installed from the .exe installer and "Hide file extensions for known file types" remains checked in Windows Explorer. You can unhide extensions on Windows by following these instructions.

Audacity's project format is not compatible with and cannot be opened in any other audio program.

The project file describes how Audacity links these AU files together to make up the clips and tracks in the project; it also contains gain, pan and envelope information, data to manage the waveform display and carries links to any dependent audio files being read directly from their source location.

The AUP file is in XML format and can be opened in a text editor if required. The AU files are stored in a lossless, uncompressed format. Their default size is 1 MB or less. This Audacity Project Format is designed to make editing audio faster in Audacity. By updating individual AU files during editing, Audacity can change audio or move it around in the project without copying large quantities of data from one place to another.

The four rules for keeping your Audacity Project happy:

When importing an uncompressed audio file with the "Read uncompressed file directly from the original (faster)" option checked in Import / Export Preferences never move, rename or delete that file unless you first copy it into the Audacity project. See File > Check Dependencies for more information.
Never move, delete or rename any of the files or folders inside the _data folder.
Never rename the AUP file or the _data folder.

Always keep the AUP file and the _data folder together in the same directory (folder).

Opening an Audacity project

When opening an Audacity project always use File > Open or File > Recent Files to open the "my_song.aup". Do not attempt to open, import or manipulate any individual AU files.

Audacity can open .aup files created in 1.2 versions of Audacity, but if you save the file after opening it, it will no longer open in 1.2.
Projects created by Audacity 1.1.x or earlier are no longer supported. To opens such projects in Audacity, export each audio track as WAV using the appropriate legacy version of Audacity, then import the WAV files into the current version of Audacity.

Audio which was not saved as an Audacity Project will need to be imported using File > Import, File > Open or by dragging the file in. The Import command is used to import audio data into an already open project, whereas the Open command used on an external audio file either imports the file into the current project if it never contained any other tracks, otherwise imports it into a new project window. See Importing Audio for more information.

Project Dependencies

When importing uncompressed audio files, such as WAV or AIFF, Audacity has an import preference that lets you save disk space and edit the files almost immediately by reading them directly from their original source location, rather than copying them into the project. In that case Audacity will refer externally to the original file as it manipulates the audio data within the project (while not ever making any changes to that audio file unless it is told to do so). If you read the files directly, you must not rename, move, delete or overwrite those original source files.

On the first use of the File > Import > Audio command to import un-compressed audio, the preference is set to "copy in" and a dialog is presented explaining the difference between copy-in and read-directly and asking which method should be used. See Warnings Preferences for an example of the warning dialog.

When a project is saved, and the "faster" option has been chosen in Import / Export Preferences, Audacity will display a dialog box showing these dependencies and give the option of copying all of the audio data into the project making it independent of external audio files and making it safe to delete, move or modify the original audio files if necessary. The Projects Preferences settings can be modified so that Audacity will not ask but will always either "never copy" the dependent audio files, or "always copy" them into the project on exit from Audacity.

At any time it is possible to click on File > Check Dependencies... to see if the project depends on any external files.

Import settings: "faster" versus "safer"

There are two settings available to control the manner in which the File > Import command operates.

The safer option: This is the more secure option to choose, meaning that Audacity will always have its own copy of imported files to work with. It is the default setting for audacity. Choose this option if the Audacity project file is required to be opened on another computer, or to be sent to someone else. This option need not be chosen if an exported audio file like an MP3 or WAV file is to be sent to someone else.

The faster option: When this option is selected Audacity can use its On-Demand Loading to operate faster and save disk space. Import of the audio will usually be faster, but Audacity will depend on the audio file remaining accessible and having the same name and location as when you imported it. The audio file is not actually imported or copied into the project in this case, rather it is accessed as an external file by Audacity.

It is important to understand the implications of using the faster import setting; if this is selected then it is crucial that any uncompressed audio file on which your project depends is not moved, deleted or renamed. If plenty of disk space is available and the time taken to make the full import is not an issue, then it is strongly recommended that this Preference be set to the safer option. This way the project will then always remain independent of external audio files.

Saving an Audacity Project

There are two main commands for saving projects:

File > Save Project saves an .aup project file and a _data folder containing the actual audio.
File > Save Project As... is for saving an empty project or to save an existing Project to a new name.

This saves or updates the .aup file and _data folder. Saving a project lets you save unfinished work and re-open it later in Audacity exactly as it was, with all edits and recorded/imported tracks preserved. As with saving any type of file, certain characters cannot be used in the name of the .aup file if they are reserved for the operating system; see our information on forbidden characters.

A saved Audacity Project can only be opened and used by Audacity if you want an audio file that will play on your music player or to burn a CD then you will need to Export one.

Some benefits of saving a project:

No need to re-import or re-record files
Fast loading, even of multiple long tracks
Audio data is always preserved in lossless quality. This is useful if you have already exported to a lossy audio format like MP3 but decide to edit the project further. Editing and re-exporting the project saves the additional quality loss of re-editing the previously exported MP3.

When saving an Audacity project it is normally easiest to use the File > Save Project command, which has a default shortcut of CTRL + S (or COMMAND + S on Mac). If you save a project again having made further changes to it, "Save Project" then updates the .aup file and _data folder silently without bothering you with prompts.

If the project does not have any unsaved changes (for example, if the project is empty or you just saved it), "Save Project" will be grayed out. In that case, use File > Save Project As... instead. "Save Project As" is the safe and recommended way to make a copy of a project with a new name or location. This could serve either as a single backup copy of the project, or as one of several incremental copies of the project in the state it had at a particular date and time. If you "Save Project As" with a new name, the project window then displays the project name you just "saved as". The project window displaying the project as previously named is closed, but can be reopened as required.

There is no need to save a project, unless required, as it is possible to work with temporary project files and then just Export the required audio files. If the project is not saved, the necessary audio data is stored in the temporary folder specified in the Directories section of Preferences until exiting the program. At that point, Audacity offers the choice of saving a project or not.

Exporting audio files

To make an audio file for playing on your music player, burning CDs or for use in other programs you must use one of the Export audio commands as Audacity projects can only be opened and used by Audacity; neither the .aup project file or the .au files in the _data folder can be used in other programs or devices.

Use File > Export... which brings you to the File Export dialog; here you can select from various standard audio file formats according to your purpose.

The two most common formats which can be played almost anywhere are:

WAV: a lossless very high quality, but large, format ideal for burning to Audio CDs. WAV files will open, play and can be edited on Windows, Mac OS/X and Linux computers.
MP3: a lossy lesser quality format but small enough to send over the Internet or store on portable devices. Typically an MP3 file can be around ten time smaller than the equivalent WAV. They will also open and play on Windows, Mac OS/X and Linux computers. MP3s are good for listening and sending or web posting but are poor for editing and production.

To export as MP3, don't forget to add the LAME MP3 library to your computer. Add the FFmpeg library to your computer to export to AAC or WMA which are used in iTunes and Windows Media Player respectively.

Moving or sending an Audacity project

Moving Audacity projects can be tricky due to their complex structure as described above. Any project can be moved on the same computer by making a copy of the project with the File > Save Project As... command.

Sending somebody just an AUP file does not send them an Audacity project - to do that you would need to send the folder with the data files too.

For a simple single track project (that does not have gain or pan settings, or use an envelope to adjust the volume) one possible solution is to not to move the project. Instead, use the File > Export command to export a WAV file. This WAV file can then be copied to another computer, then the File > Import command can be used to load the WAV file into an Audacity project. Alternatively the WAV file can be sent by e-mail or via a file sharing web site to someone else who can import it into an Audacity project on their computer.

For a project that has multiple tracks, or a single-track project that has gain or pan settings or uses an envelope to adjust the volume of the track, the entire project will need to be moved. To do that it is necessary to move the AUP file <my_project_name>.AUP and the _data folder <my_project_name>_data either to a second computer or to a different location on the existing computer. Ensure that the .aup file and _data folder remain together in the same folder.

As noted above, any project can be moved to a different location on the same computer using the File > Save Project As... command.

If you want to move a project to a different computer the project must not depend on external audio files. Use the File > Check Dependencies... command to check whether the project depends on any external files. If it does, the dialog box will give you the option to make a copy of those files within the project.

It can be difficult to e-mail complex projects to other users; to do so it is necessary to zip up the entire project structure and e-mail or share that zip file. The reason for zipping up the project is to make sure the project structure remains intact during the transfer, not to save space. A zip archive of a project is likely to be about 10% smaller than the unzipped project.

External files have absolute references in the AUP file and thus it is difficult to move an Audacity project that depends on external files to another computer but relatively easy to move a project to a different location on the same computer. See this article in the Wiki on Sending your work to others.

Deleting an Audacity project

There is no File > Delete Project command in Audacity; therefore to delete a project to free up disk space it is necessary to make the deletion manually. You will need to delete both the AUP file and its associated, identically named _data folder.

Note that this will not remove the listing of your project under File > Recent Files.... After deleting the project you can choose the AUP entry for that project in the Recent Files list in order to remove the entry.

Autosave and Recovery

Audacity has an automatic saving system running in the background so as to provide efficient project recovery in the event of a crash or power loss. As soon as you open a project window and add or change the window contents, Audacity writes a temporary reference file for the project called an autosave file. This file is stored in the "AutoSave" folder inside Audacity's folder for application data.

The autosave file is structured identically to a saved .aup project file, but exists at any time there are unsaved changes to a project, namely:

If you have not yet saved an .aup project file (in which case the audio data itself is still stored in Audacity's temporary directory)
If you have already saved an .aup project file but made subsequent changes (in this case, the audio data itself is stored and always remains in the _data folder that has the same name and location as the .aup file).

Changes to the audio data are always autosaved. The autosave file is also modified to reflect positional changes, such as moving the cursor or selection region or changing the track height, although such changes are not stored in the project's Undo History.

If a crash or power loss does occur, Audacity when restarted will display the Automatic Crash Recovery dialog. A list is provided of projects that can be recovered, one project for each window that had unsaved changes. Be sure to save the project before closing it, or all the unsaved changes will be lost.

Disk space usage

This can be particularly important if you are editing a large project.

Audacity references the original audio material until you actually perform some kind of edit on it, such as cutting a piece away or using any effect on it. So if you Edit > Duplicate a selection, this doesn't actually increase the number of .au files in the _data folder, and doesn't increase disk space usage. Edit > Copy for example does increase the number of .au files, but this is so these files can be retained separately on the Audacity clipboard for Edit > Paste.

Once you perform an edit, the original unchanged audio is retained, along with the changed audio. This is so you can use Edit > Undo and Edit > Redo to try out edits and undo them if they don't sound as you wanted.

If you edit just a small selection in a track, only that small selection of changed data is written to disk. Nonetheless, this still represents a doubling of disk space usage for that selection, and a further edit on that selection (unless you first undo the previous edit) represents a quadrupling of disk usage. For example, a five minute stereo recording at default quality settings takes 100 MB of space. If you edit the whole length of that recording, disk space usage will increase to 200 MB.

If disk space is a problem while working on a project, you can use View > History... to discard Undo levels and reclaim disk space. Note that once you close the project by using File > Close or exiting Audacity, the audio data needed for Undo/Redo is discarded, so as to make project storage as economical as possible.

Any audio data placed on the Audacity clipboard by Cut or Copy is however retained until you exit Audacity itself.