Speaking of Mathematics
Audio formatting makes much information accessible, but not necessarily digestible. Raman writes: "The passive printed document is processed by an active reader, who can view it in many different ways—read only section titles, skip a piece of mathematics, temporarily skip to a different page to read a referenced theorem, reread an interesting passage, and so on . . . . When it comes to audio,
on the other hand, the document is the active player and the human is the passive one. The speaker (perhaps on an audio cassette) actively reads in a relentlessly linear fashion, from beginning to end, and the listener simply listens, with little control over the process."
AsTeR gives a measure of control back to the listener. The key to this capability is the treelike internal representation of the text, which describes both the details of mathematical expressions and the larger-scale architecture of the entire document, with its headings and subheadings and other structural markers. Keyboard commands allow for quick navigation through this tree, with much greater flexibility than the fast-forward and rewind controls of a tape player. You can skip from one subhead to the next within an article, or from one term to the next within an equation, then delve into any selected structure
in greater detail.