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Posted on 21 Sep 2005 at 17:01

Brian Heywood looks at cost-effective ways of capturing the sound of music safely onto your computer's hard disk

However, since Cool Edit was snapped up by Adobe and transmogrified into Audition, this option has disappeared, although you may well find an old copy squirrelled away on the Web somewhere. Since then, I've been keeping my eye out for a decent replacement, and I may just have found one in the shape of Audacity. This is a freeware editor developed by volunteers from the open-source community (sourceforge.net) and distributed under the GNU General Public License (GPL). This means that as well as getting a ready-to-run audio utility, you can get your hands on the source code, either to study or to augment it to suit your purposes.

Unlike the free software you often get bundled with your PC or sound card, Audacity is a genuine multichannel editor, which makes it more akin to Audition, Nuendo or SoundForge than to the original Cool Edit shareware program. It means you can record new audio in sync with pre-recorded material, or else build up a track one instrument at a time. While recording, you can monitor the new track both visually and audibly as you play it in. As you might expect, there's the usual latency delay due to the software and the operating system, but the magnitude of this timing error will depend on how powerful your PC is and on the quality of your sound card's device drivers, and it can be easily corrected in the audio editor.

One really novel aspect of Audacity is tucked away in its Effects menu, where there's an option called 'Nyquist Prompt...' Nyquist turns out to be a Lisp-like programming language written by Roger B Dannenberg and is designed to be a complete programming language for audio synthesis and analysis. The full programming language looks like it's pretty comprehensive, with support for MIDI, audio recording and playback, file I/O, object-oriented programming, profiling, debugging and so on. Audacity uses a cut-down version of the language, without the debugging facilities, to give you a way of processing your audio from a command-line interface. In fact, you can use it to write your own plug-ins to customise your audio processing, or even generate audio from scratch.

To roll your own plug-in, simply create a text file with the extension '.ny' in Audacity's plug-ins directory. This file, which you can create with any text editor, will contain some Nyquist code, along with comments to indicate the type of plug-in and what it does. Next time you load Audacity, your new plug-in will appear in either the Generate, Effects or Analyze menu (depending on the program code) ready for use. This aspect of the program will ensure Audacity stays on my PC's desktop alongside my other audio-processing software. You can also get the full Nyquist package from the Carnegie Mellon University Computer Music Project (www.cs.cmu.edu).

This application looks useful, even if you already have a favourite production editor. You can download Audacity for free from http://audacity.sourceforge.net or find it on this month's cover disc.