Audio layout is achieved by super-imposing fleeting and persistent cues on the rendering. To convey nesting effectively, the AFL state changes used to achieve persistent cues need to be monotonic in the mathematical sense. Let [tex2html_wrap5632] represent a point in audio space. Let [tex2html_wrap5634] be a change-of-state function. To convey nesting effectively, [tex2html_wrap5636] should be monotonic -there should exist an ordering
where this ordering is perceptible. This is where we exploit the abstraction of a speech space and the operators it provides. For instance, the following AFL statement can be used to define a function that generates new AFL states for rendering itemized lists:
[LVerbatim1335]
This notion of monotonicity in change of AFL states will be exploited once again in s:math_readings when designing an audio notation for mathematics.