Microsoft AI: MAI-Voice-2.1-Flash

MAI-Voice-2.1-Flash is a low-latency text-to-speech model from Microsoft AI, optimized for real-time responsiveness. It produces natural, expressive speech across 23 languages, with human-like intonation, rhythm, and emotional nuance. It is suited for voice agents, assistants, call centers, and other interactive applications where latency and cost matter most. On OpenRouter, set `voice` to a full voice ID with the model suffix, such as `"en-US-Harper:MAI-Voice-2.1-Flash"`. A voice's locale sets the synthesis language. Set `response_format` to `"mp3"` or `"pcm"` (24 kHz mono). Harper and Grant support the `agent`, `customer-call-center`, `educational`, and `narrator` speaking styles, and many locale voices add emotion styles such as `excited`, `happy`, `sad`, and `whispering`. The full list of voices is in the `supported_voices` field of the models API. See the text-to-speech guide.