W3C CSS2 Cascading Style Sheets, level 2 - instructional media + ...

Example(s):
The following two rules are equivalent:
H1 {cue-before: url("pop.au"); cue-after: url("pop.au") }
H1 {cue: url("pop.au") }
If a user agent cannot render an auditory icon (e.g., the user’s environment
does not permit it), we recommend that it produce an alternative cue (e.g.,
popping up a warning, emitting a warning sound, etc.)
Please see the sections on the :before and :after pseudo-elements [p. 153] for
information on other content generation techniques.
19.6 Mixing properties: ’play-during’
’play-during’
Value: mix? repeat? | auto | none | inherit
Initial: auto
Applies to: all elements
Inherited: no
Percentages: N/A
Media: aural
Similar to the ’cue-before’ and ’cue-after’ properties, this property specifies a
sound to be played as a background while an element’s content is spoken.
Values have the following meanings:
The sound designated by this is played as a background while the
element’s content is spoken.
mix
When present, this keyword means that the sound inherited from the parent
element’s ’play-during’ property continues to play and the sound designated
by the is mixed with it. If ’mix’ is not specified, the element’s background
sound replaces the parent’s.
repeat
When present, this keyword means that the sound will repeat if it is too short
to fill the entire duration of the element. Otherwise, the sound plays once
and then stops. This is similar to the ’background-repeat’ property. If the
sound is too long for the element, it is clipped once the element has been
spoken.
auto
The sound of the parent element continues to play (it is not restarted, which
would have been the case if this property had been inherited).
none
This keyword means that there is silence. The sound of the parent element
(if any) is silent during the current element and continues after the current
element.
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