linguist

A century later, and after a few revisions, it’s now used around the world by linguists, but also phonologists, speech pathologists, singers, and loads more people.

The ones with white backgrounds are possible for humans to make, but they've not been given a symbol, because linguists have never found them actually being used as sounds in any of the world's languages.

James Lovelock, one of the last independent scientists, born in 1919, back when "scientist" could be an entire job description rather than "botanist" or "physicist" or "computational linguist".