Eleven Labs announced that it would soon release a synthetic voice generator that "lets you set certain basic parameters which establish the new voice's core identity: gender, age, accent, pitch and speaking style. In other words, every time you hit 'generate', even if you choose the same base parameters, you get a completely new voice that didn't exist before."
You can listen to a few different samples here. They sound really good. As Eleven Labs says, these voices can be used to narrate books, video games, ads, and articles.