Use the Macintosh speech synthesizer to speak a message.
speak “the message to speak”
OR
say “the message to speak”
the say variant allows adding the optional in (number, seconds to schedule the speech for) parameter.
speech is asynchronous, the script continues immediately and the speech continues in the background. If many phrases to speak overlap they are queued up and spoken one after another. If you accidentally queue up a large number of phrases you can use the Stop Speaking verb to clear the queue.