The free audio editor Audacity is highly popular in open source music circles. Users rely on Audacity for radio productions, podcasts, and video soundtracks – on Windows and Mac OS as well as Linux. Others use Audacity to digitize cassette tapes and vinyl records. However, many professional musicians have never really been satisfied with Audacity.

The most common criticism of previous Audacity versions was that Audacity didn't allow you to set parameters for effects during playback. With version 2.1, Audacity is now beginning to eliminate this weakness (Figure 1). Additionally, the new version offers many more functions and unique new techniques for sound editing in Linux.

Figure 1: Audacity 2.1 lets you configure effects while the editor is playing the track.

Unpacked

Audacity 2.1 has been available on the project website [1] since the end of March 2015. You'll find installer packages for Windows and Mac OS X; Linux users will find only source code at the Audacity site; check your distro's software repository to see if the latest version is available in package form. The complex Audacity with its cross-platform functional interface has a long list of dependencies. When I tried to build Audacity from the source code on Ubuntu 14.04 LTS, the configure step worked, but the Make build process aborted with an error.

Other Ubuntu administrators have obviously had more luck. The new version was online in the Audacity team's PPA repository a few days after the release [2]. However, because the new PPA version only contains daily builds, you might want to use the PPA maintained at the UbuntuHandbook.org blog [3]:

$ sudo add-apt-repository \
  ppa:ubuntuhandbook1/audacity
$ sudo apt-get update
$ sudo apt-get install audacity

The most important components included with the package are:

• Alsa and OSS as an audio interface,
• Jack as an audio interface via PortAudio,
• Built-in effects, Nyquist console plugins, and Vamp plugins (for visualization)
• LADSPA and Linux VST (lxvst) effects in real-time (lxvst with graphical user interfaces)
• LV2 effects (still without the GUI and not adjustable in real time).

Audacity 2.1 is also available for other common distributions. Fedora is introducing the version to the official package sources from Fedora 20. Packman [4] offers packages for openSUSE back to version 12.3.

Audacity 2.1 launched quickly in my tests, which ran on Ubuntu 14.04 with the KX Studio extensions [5]. Despite the many new functions, the new version is still remarkably stable. Whenever things went wrong in the lab, the problem appeared to be a problem with a plugin.

The Carla VST plugin did not work at all and caused Audacity to crash. Other plugins reacted badly to extreme settings: TAL-Reverb crashed as soon as the section playing live reached the end. Automatic recovery took effect each time Audacity was unresponsive when an error occurred. The automatic recovery feature opens a dialog when you launch Audacity for the first time after a crash. During testing, virtually no modifications that I failed to save before the crash were lost.

Audacity also uses the interface available on Windows and Mac OS X PortAudio [6] for the connection to Jack. This connection now works without any nasty scratching noises or noticeable delays but still remains inferior to a native connection to a Jack server. PortAudio thus only generates a port in Jack, for example, if Audacity is currently playing or recording something. The ports always receive new names. Editing the output from Audacity with external Jack software is a bit of a hassle because Audacity can only be patched while running.

The situation looks better for recording from Jack sources. Audacity lists Jack sources in its summary of recording devices, top center (Figure 2). However, these applications need to be running when you start Audacity; Audacity simply ignores Jack sound sources launched during the Audacity session.

Figure 2: Audacity does not record from multiple Jack sources at the same time. However, you can record Jack sources one after the other without a problem.

Unlike many other multitrack recording studios, you do not have to configure a track for a new recording yourself in Audacity. The program automatically creates it for you when you press the red record button. However, this design means that only one recording is possible on each track. This approach allows faster and more intuitive work than more demanding software recorders.

Imports and Exports

You can import audio material from supported files directly into the current project as a new track. Audacity needs the corresponding external libraries to open MP3 and similar formats. A meta-package such as ubuntu-restricted-extras will provide you with a collection of important codecs.

Audacity always converts all audio data formats into the uncompressed ULAW-AU format for editing. ULAW-AU corresponds almost completely to similar formats such as Microsoft's WAV or Apple's AIFF. You can import audio tracks from video files. Audacity uses Ffmpeg (libavformat); you will need to install a suitable version. Enable a multichannel mix tool in Edit | Preferences | Import/Export for exporting formats with surround sound.

The versions of Ffmpeg available in Ubuntu caused Audacity a few difficulties in the test. The Audacity package from the Audacity team's PPA requires libavformat.so.55, whereas the package sources from Ubuntu 14.04 LTS only provide version 54. Audacity also refused to use version 56 of libavformat built from the current source code; I thus had to do without the Ffmpeg functions.

To load an audio track into a new instance, you use File | Open. All running instances of Audacity share the cache. You can copy sections of a recording from a running instance using Ctrl+C and then paste them into another project using Ctrl+V (Figure 3).

Figure 3: When working with multiple open instances, it is immensely helpful that the Audacity interface can be set to be very small – despite its many functions.

The File | Export Audio option lets you export completed projects. Just below, you will find several other export functions for selecting or outputting multiple files. However, the MIDI export offered here counts as the very first step toward MIDI support: As before, Audacity cannot really do anything practical with MIDI; however, the export function at least lets you get started.

At the bottom right of the export tool you can select the desired format for an export. Audacity uses WAV PCM by default for 16-bit files. Audacity does not offer to convert the sample rate when exporting, so if you are working on a video soundtrack, you should make sure the project is running at 48kHz. (44.1kHz is standard for CD audio.)

Select Other uncompressed files, and you'll see a very long list with various niche formats if you click on Options (Figure 4). Some of these formats are reason enough for an aspiring sound engineer to install Audacity: The application provides proud owners of an Akai sampler the option to export home-made drum sounds into the MPC format.

Figure 4: Many of the audio outputs supported by Audacity allow the configuration of the bit depth and other header parameters.

Listen Here and Now

The main improvement in Audacity 2.1 is the real-time mode for effects. Previous versions only allowed a brief preview when setting the parameters of effect plugins, and you could not move the sliders. This limitation made Audacity unattractive for serious ventures.

Using real-time mode, you can now change the different parameters in all Linux VST and LADSPA modules, and you can listen to the effect of the changes immediately. Additionally, Audacity's Effects window provides buttons for controlling the drive (Figure 5). You can save and load the settings with the Effect | Manage menu item when you need them.

Figure 5: Effects such as TAL-Reverb in its Linux VST version provide default settings that can be selected using the inconspicuous button to the left of the drive keys.

You can enable and disable the effect formats LADSPA, VST, and LV2. To avoid problems with experimental plugins, you should manage them in separate directories and link them to /usr/lib or /usr/share/audacity/plug-ins/, depending on the distribution. Please note: Nothing caused as many problems in the tests as running external effects, although the built-in plugins worked perfectly and safely.