From CCRMA Wiki
Written and developed at CCRMA by Bill Shottstaedt, SND is a sound editor modeled loosely after Emacs, an old, sorely-missed PDP-10 sound editor named Dpysnd. It can accommodate any number of sounds each with any number of channels, and can be customized and extended using guile and Ruby. It can be customized and extended using either s7 (included in the Snd sources), Ruby, or Forth. Snd can be started on any PlanetCCRMA Linux workstation by selecting the application on the PlanetCCRMA menu and the editors tab. Otherwise SND is started by typing the 'snd' command on a terminal window or shell.
To get started, go to the file menu, and open a sound file. To hear the sound, click the 'play' button. To see an fft, click the 'f' button on the left. The left mouse button is used for most pointing operations; the middle button pastes in the current selection; the right button brings up the SND pop up menu. Make sure you go through the help pull down menu to find more about all the features SND. In addition to this there is an enormous amount of information in the snd manual or search its documentation on its index