Wow, interesting and relevant case! I am very narrowly on the side of Midler here, only because they ALSO used her song (and even though the copyright owner of the song agreed to it). I don't think OpenAI's use of the other voice actress falls under the purview of this case though.
If I was defending such a case (IANAL), I'd hire 10 voice actresses of the same age and record them saying the same thing and see if the jury could detect the differences among them and to what degree.
If I was defending such a case (IANAL), I'd hire 10 voice actresses of the same age and record them saying the same thing and see if the jury could detect the differences among them and to what degree.