Implemented under MacOS only
Scalar number in the range ¯1.0 to +1.0
Valid for: Movie
Set movie volume in range ¯1.0 to +1.0. Values between 1.0 and 0.0
cause sound to be reduced proportionately. Negative values mute the sound
and can be used to stop the sound temporarily whilst retaining information about the
volume previously chosen.