# Chains - for batch processing and effects automation

### From Audacity Manual

A Chain is a sequence of preconfigured commands in a set order (mainly effects) that can be applied automatically to projects or audio files. Any built-in or Nyquist effect shown in the Effect Menu and export commands can be added to a Chain.

## How to use Chains

There are two related Chain commands in the File Menu called Edit Chains and Apply Chain. Look first at Edit Chains to determine if an existing Chain (Audacity only ships with one) will suit your needs or to create a new chain. Next, use Apply Chain to perform the action on your selected audio.

The two uses of Chains are for:

- Batch processing (where many audio files are processed unattended with one or more effects then exported to a new file)
- Effects automation (where the selected audio in the track or tracks in the current project is subjected to the same prescribed sequence of effects, and optionally, a file exported from the entire audio.)

See the examples below.

## Edit Chains

Use File > Edit Chains... if you need to create a new Chain or to edit an existing Chain.

- The Chain can include a number of common Audacity functions and effects to be executed in any order you specify.
- To create an audio file as part of the Chain process you must include an "Export" command (such as ExportWAV).
- In many cases the parameters for each command in the Chain can be specified within the Edit Chains dialog.

The left hand box in the dialog (labeled Chains) contains a list of already defined Chains. Until you add a new Chain, it only has a single built-in "MP3 Conversion" Chain. You can:

- Use the Add button to create a new Chain
- Use left-click (or use the Up or Down arrow on the keyboard) to select the Chain you want to work on
- Delete any user-added Chain with the Remove button
- Rename any user-added Chain with the Rename button

The Remove and Rename buttons are greyed out when the MP3 Conversion Chain is selected.

The right-hand box (labeled Chain) lists the ordered sequence of commands for the Chain selected in the "Chains" box on the left. You can:

- Add or remove commands for the selected Chain
- Change the order in which the commands execute in the Chain
- Edit the parameters for some effects in the Chain

For further details see the Edit Chains page.

## Apply Chain

Use File > Apply Chain... to show the existing chains. Select the chain you require by using left-click (or using the Up or Down arrow on the keyboard) to select the Chain you want to work on, then either:

- choose Apply to Current Project to run the Chain on the entire project in the current window or
- choose Apply to Files to run the Chain on selected external audio files in a single directory

  Accessed by: File > Apply Chain...

| If you already have audio in the current project window, you must save and close that project using File > Close before applying a Chain to files.

For more details see the Apply Chain page.

## Chain Examples

In this section we look at a couple of examples of how a Chain might be used. In the image below we have added two additional Chains. It is important to note that the only Chain that Audacity ships with is MP3 Conversion (shown as selected in blue). All other Chains must be added by the user.

### Example 1: LoudMP3

A batch processing Chain to compress and normalize WAV files then convert them to MP3:

1. Use Compressor to reduce the dynamic range of each WAV, also normalizing them to maximum amplitude of 0 dB
2. ExportMP3 then converts them to MP3 format.

### Example 2: NR&EQ

An effects automation Chain for the current project that applies noise reduction and equalization:

1. Normalize with settings of:
   - Remove any DC offset
   - -10 dB (to allow for boosting frequencies later in the Chain without clipping)
2. Noise Removal
3. Equalization (to perform the frequency adjustment)
4. Normalize again at different settings (without offset removal, setting a final amplitude of -1 dB).

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