The advent of electronic documents makes information available in more than its visual form —electronic information can now be display-independent. We describe a computing system, AS TE R, that audio formats electronic documents to produce audio documents. AS TE R can speak both literary texts and highly technical documents (presently in (LA)TEX) that contain complex mathematics.

Visual communication is characterized by the eye’s ability to actively access parts of a two-dimensional display. The reader is active, while the display is passive. This active-passive role is reversed by the temporal nature of oral communication: information flows actively past a passive listener. This prohibits multiple views —it is impossible to first obtain a high-level view and then “look” at details. These shortcomings become severe when presenting complex mathematics orally.

Audio formatting, which renders information structure in a manner attuned to an auditory display, overcomes these problems. AS TE R is interactive, and the ability to browse information structure and obtain multiple views enables active listening.