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3.2 Audio Formatting And Aural CSS

AsTeR introduced the notion of audio formatting a concept analogous to the well-understood notion of visual formatting. The work on AsTeR coincided with the Web being at its infancy. As the Web evolved to acquire Cascaded Style Sheets (CSS), ideas from AsTeR were used to define Aural CSS as an appendix to CSS1 in 1995. Emacspeak proved an ideal platform to prototype the ideas within Aural CSS — first within the Emacs/W3 browser. Around this time, Emacs itself evolved to support multiple fonts and font-locking to implement syntax coloring for various types of content. Emacspeak applied the ideas of audio formatting to create the auditory analog of font-lock — Emacspeak calls this voice locking.

Voice locking in Emacspeak continues to be a unique feature among systems that provide auditory feedback. Later in 1997, Emacspeak’s implementation was overhauled to use Aural CSS for all aspects of voice-locking, rather than just for Web content.