Yeah, or if we had generic attributes we could do:
{type=audio}
There was also some discussion in the generic directives thread as to whether something like this should be rendered as a block or inline element. The tentative conclusion was that :audio[my title]{src=music.php} should be rendered inline (even if the markdown processor doesn’t know the audio directive/extension it would generate a <span> which postprocessor or js could pick up), and with two colons it should be rendered as a block (a <div> if extension unknown):
::audio[my title]{src=music.php}