When reading complex mathematics in print, we first get a high-level view of an equation and then study its various subexpressions. For example, when presented with a complex equation, an experienced reader of mathematics might view it as an equation with a double summation on the left-hand side and a double integral on the right-hand side, and only then attempt to read the equation in full detail. In a linear audio rendering, the temporal nature of audio prevents a listener from getting such a high-level view. We compensate by providing a variable-substitution rendering style. When it is active, AsTeR replaces sub-expressions in complex mathematics with meaningful phrases. Having thus provided a top-level view, AsTeR then renders these sub-expressions.