Configuration of how speech should be synthesized.
Optional. Speaking pitch, in the range [-20.0, 20.0]. 20 means
increase 20 semitones from the original pitch. -20 means
decrease 20 semitones from the original pitch.
Optional. An identifier which selects 'audio effects' profiles
that are applied on (post synthesized) text to speech. Effects
are applied on top of each other in the order they are given.