In general, TeX macros can perform any arbitrary computation permitted by TeX, a Turing-complete language. Hence, it is impossible to directly translate the macro expansion into an audio rendering. The TeX primitives are visual layout operators, and translating a TeX macro directly into an audio rendering rule would imply a one-to-one mapping between the visual and audio rendering. As explained in s:introduction, visual renderings are attuned to a two-dimensional display, and audio renderings need to be attuned to an auditory display. Further, expanding a TeX macro loses structural information; when all macros in a document have been expanded, only the visual layout remains.