40.10 Sound Output

To play sound using Emacs, use the function play-sound. Only certain systems are supported; if you call play-sound on a system which cannot really do the job, it gives an error. Emacs version 20 and earlier did not support sound at all.

The sound must be stored as a file in RIFF-WAVE format (`.wav') or Sun Audio format (`.au').

Function: play-sound sound

This function plays a specified sound. The argument, sound, has the form (sound properties...), where the properties consist of alternating keywords (particular symbols recognized specially) and values corresponding to them.

Here is a table of the keywords that are currently meaningful in sound, and their meanings:

:file file

This specifies the file containing the sound to play. If the file name is not absolute, it is expanded against the directory data-directory.

:data data

This specifies the sound to play without need to refer to a file. The value, data, should be a string containing the same bytes as a sound file. We recommend using a unibyte string.

:volume volume

This specifies how loud to play the sound. It should be a number in the range of 0 to 1. The default is to use whatever volume has been specified before.

:device device

This specifies the system device on which to play the sound, as a string. The default device is system-dependent.

Before actually playing the sound, play-sound calls the functions in the list play-sound-functions. Each function is called with one argument, sound.

Function: play-sound-file file &optional volume device

This function is an alternative interface to playing a sound file specifying an optional volume and device.

Variable: play-sound-functions

A list of functions to be called before playing a sound. Each function is called with one argument, a property list that describes the sound.