Oh man, I can already see the court cases of a certain robot's voice sounding a little too similar to a deceased human's that it should make royalty payments.

Heh, in my original post I wanted to follow up that paragraph with a question: Is someone's voice their IP?

Would e.g. Don LaFontaine's family go all J.R.R. Tolkien and forbid the use of his voice in certain contexts?

Then again, for now, it seems that it's easy to get away with synthesizing voices of popular characters as long as you don't use copyrighted names:

https://acapela-box.com/AcaBox/index.php

(choose English(USA) - "Little Creature". Borked on Firefox but works in Chrome)

"Little Creature" my ass.

Apparently, names are IP, voices not so much. But we can't have nice things because like you said - eventually, someone's going to figure out how to file an effective lawsuit.

I don't see it as being very different than using someone's face to promote something.

For example, should a lifelike digital model (or even a still image) of an actor's face still generate royalties for the actor's family after their death? Both cases are using a unique attribute of the person to promote something.

I don't think voices are copyrightable, but the recordings used to analyze them are, and so the resulting voice might be considered a derivative work.

I can't tell if that's Yoda or Cookie Monster.

https://lyrebird.ai/ and Adobo VoCo are two products which can take a small sample of a persons voice then generate any words/sentences in their voice