This statement sends text to the speech device. In addition, the speech component provides primitives for producing the right intonational structure. The speech generation statements are summarized in t:speech-events.
The speaking voice can be varied with respect to several speech synthesis parameters. We define the speech space as a multi-dimensional space, where each dimension corresponds to a synthesizer parameter. At any given time, the speech state, a point in this space, determines the kind of voice used when speech generation statements are executed. Changing a voice parameter amounts to moving in this space. The abstraction of a speech space imposes structure on the set of discrete states provided by the voice synthesizer. This structure will be used to advantage in producing renderings of nested information structures. The abstraction of a speech space also keeps the speech component of AFL hardware independent -synthesizers vary widely in both the kind of parameters provided as well as how these are modified.
In any AFL program segment, global variable *global-speech-state* and local variable *current-speech-state* (modifiable by the program segment) refer to one of these speech states. When a session of interactive rendering is begun, these variables are set to the initial state of the audio formatter.