Another option is Acoust, which uses large neural language models to generate natural-sounding audio. It's got a free tier and a range of customizable controls, emotions and options like speech-to-text transcription. It's good for a variety of uses, including social content, explainer videos and IVR, so it's a good option if you have a variety of content needs.
If you need a broader range of voices, BeyondWords has more than 550 AI voices across 140 language locales. It's got a full audio content management system and lots of options for customization, so it's good for articles, newsletters and blog posts. The company offers a free Pilot plan if you want to get started without spending money.
Last, Narration Box offers high-quality, natural-sounding voiceovers in 140+ languages and accents. It's got a block-based interface that's easy to use and a library of more than 700 AI narrators, and a free tier with 1,000 text-to-speech words. It's good for e-learning, product demos and audiobooks, and has a range of options for customizing your content.