A modal prompt display means that the prompt item is shown, but marked as inactive, e.g. by using greyed-out text, low resolution images or a disabled audio button. The default setting is to have modal prompt display during the prerecording and postrecording phases, and an active prompt display during recording. The attribute promptphase of a <section> element determines the start of an active prompt display, and it overrides the default setting.
A prerecording phase is useful to either record environment noise prior to the main recording, or to give the speaker a precisely delimited time to prepare the utterance. A postrecording phase is most commonly used to avoid signal truncation due to clicking the stop button too early.
The timing for time-dependent prompts has to be set to appropriate values by the script author, e.g. to make sure that the recording time is sufficient for prompt playback and recording.