The Linux Soundfile Editor Roundup

Dozens of other operations can be added to this list, and each user will find special uses for a soundfile editor.

Slowing the playback speed of a file without changing its pitch comes in handy when I am teaching. Students often bring in recordings that are not particularly easy to hear or transcribe when played at normal speed. I convert the original recording (CD or MP3) to a WAV file, load it into the Snd editor and slow the playback speed, still keeping the original pitch, until I can hear each note clearly. This makes it easier to write out an accurate transcription. Some editors let you do this in real time, and some allow a defined looping region to be arbitrarily redefined during playback, a very helpful feature.

Normalization raises the amplitudes of a file to their relative peaks, so all amplitude values are raised relative to the peak value. By normalizing my project files before burning them to CD, I balance the volume differences between pieces. Normalization is a common premastering operation in professionally produced recordings.

A soundfile editor also is useful for repairing badly formed compressed soundfiles. Some editors load MP3 and Ogg files directly, while others perform a format conversion and then load the converted file. I can remove excess silence and fix damaged spots in the recording by removing or redrawing them. The waveform display represents damaged spots as broken or incomplete curves. I also normalize and equalize the sound before converting it back to its original format. Converting a lossy-encoded file to a soundfile format and back again to a lossy format typically results in less than optimal audio quality, so I rebalance the sound's frequencies with the editor's equalization tools.

In the space allotted for this article, I can scratch only the surface of each profiled editor. We look at each program's salient aspects, but you should try each one yourself to measure the depths. Let's start this roundup with some of the older soundfile editors available for Linux.

The first wave of soundfile editors for Linux arrived at a time when OSS/Free was the system audio interface and Motif was the most attractive GUI toolkit. They were all designed to compile and run on a variety of UNIX systems, not only Linux.

Bill Schottstaedt has been crafting Snd in one form or another since the era of the PDP minicomputers. However, Snd as we know it dates from late 1996, with Linux support added in 1997. Snd is a remarkable program. It can be regarded as an exceptionally powerful soundfile editor, as an infinitely programmable audio editing toolkit or as a graphic component of the Common environment of music and sound applications. The Common family of audio applications include Bill Schottstaedt's Common Lisp Music (software sound synthesis) and Common Music Notation and Rick Taube's Common Music (metalanguage for music composition). These are all Lisp-based applications that can be configured for complex interactivity. The key to unlocking Snd's power lies in its Guile interface, based on the Lisp-like Scheme programming language. Snd's interface includes a window called the Listener in which the user can enter Guile commands for customizing and redefining every aspect of the program.

The screenshots illustrate how extensively Snd can be configured. Figure 1 shows the Motif version of Snd in its default appearance. In Figure 2, the user interface has been customized extensively. New menus have been added for Snd's internal DSP modules and LADSPA plugins, the background and colors are user-defined, and some complex widgets have been custom-built for some of Snd's effects processors. Figure 2 also shows off Snd's amplitude waveform view along with its OpenGL display of the sound's spectrum, its frequency content. Context-sensitive pop-up menus are available for the different displays as well as for selected and unselected regions of a file.

Snd is my favorite soundfile editor, but I admit that it may not be the editor for everyone. If you learn a little Lisp, you can discover more of Snd's power. Fortunately, Snd comes with exhaustive documentation to ease difficulties in the learning process. Predefined configuration files also are available for quicker and easier customization.

Figure 1. The Default Snd

Figure 2. The Author's Snd