Lists, centered text and other structures are marked up in LaTeX as special environments and are characterized by their visual layout. Thus, a list of items is cued by indenting the items in the list. Nested lists are displayed by indenting them with respect to the outer list -in audio, we use change of pitch.
An itemized list is represented internally as an object of type itemized-list, with the list of items as its children. Each item itself can be a complex object. Here is the AFL rule for rendering object itemized-list.
This rendering rule begins a block, locally sets the state of the audio formatter by raising the pitch of the voice, and then renders the contents of the itemized list. These contents are rendered relative to the containing list. When this rule is applied to a nested list, the inner list gets rendered relative to the outer list -the pitch goes up by one step when rendering the outer list, and goes up by another step when rendering the inner list. Thus, the local scope introduced by the AFL block works effectively in conveying nested structures.