Already on your Mac or PC
On a Mac, download a Premium voice in System Settings → Accessibility → Spoken Content. Select any text and press OptionEsc to hear it, or save it as audio with the Terminal command say -o speech.aiff "Your text". Windows 11 has free natural voices too, but only Narrator uses them; the free Balabolka app saves audio files with Windows' older, more robotic voices.
Piper
A free, open-source voice engine that's very fast and runs on an ordinary processor, with voices in dozens of languages. You use it from the command line or through small community apps. It doesn't clone voices, and each voice has its own licence.
Kokoro
A small free model (Apache 2.0) that sounds remarkably natural in English and a handful of other languages. Like Piper, it's mostly used from the command line or community apps, and it doesn't clone voices.
Qwen3-TTS and Chatterbox
Free open models that can also clone a voice from a short clip. They want a graphics card and a Python setup, or a free app that bundles them, such as VoiceStudio or Voicebox. How the free apps compare.
Check the licence before you publish anything: Kokoro and Qwen3-TTS allow commercial use, but F5-TTS's weights and XTTS-v2 don't.