Is there a way to get the Siri voices for NSSpeechSynthesizer? NSSpeechSynthesizer.availableVoices() does not list them, but maybe there is an undocumented trick or something?
I've also tried to use AVSpeechSynthesizer, even tough it should be available on macOS 10.14+, I couldn't get it to read out loud …
I've used a Playground to test this with the following code from NSHipster:
import Cocoa
import AVFoundation
let string = "Hello, World!"
let utterance = AVSpeechUtterance(string: string)
let synthesizer = AVSpeechSynthesizer()
synthesizer.speak(utterance)