(RFC 2046 published November 1996, subtype last updated November 1996)

A media type of "audio" indicates that the body contains audio data.
Although there is not yet a consensus on an "ideal" audio format for
use with computers, there is a pressing need for a format capable of
providing interoperable behavior.

The initial subtype of "basic" is specified to meet this requirement
by providing an absolutely minimal lowest common denominator audio
format.  It is expected that richer formats for higher quality and/or
lower bandwidth audio will be defined by a later document.

The content of the "audio/basic" subtype is single channel audio
encoded using 8bit ISDN mu-law [PCM] at a sample rate of 8000 Hz.

Unrecognized subtypes of "audio" should at a miniumum be treated as
"application/octet-stream".  Implementations may optionally elect to
pass subtypes of "audio" that they do not specifically recognize to a
robust general-purpose audio playing application, if such an
application is available.