# Expressivity for Flux TTS voices, and two new OpenAI models By Steven Van · 2026-08-19 expressivity for Flux TTS agent.speak.provider.expressivity shifts a Flux TTS voice's delivery register along a calm to animated axis. [**Deepgram**]() announced [**Expressivity for Flux TTS voices, and two new OpenAI models**]() on August 19, 2026. ## What changed expressivity for Flux TTS agent.speak.provider.expressivity shifts a Flux TTS voice's delivery register along a calm to animated axis. It accepts the whole numbers -2 to 2 and defaults to 0, the voice's tuned delivery. Negative values produce calmer, steadier delivery; positive values produce more animated delivery with a wider pitch range. Every Flux voice supports it, and the value applies for the whole session. { "agent": { "speak": { "provider": { "type": "deepgram", "version": "v2", "model": "flux-haley-en", "expressivity": -1 } } } } expressivity is a beta parameter: its behavior may be tuned in future model versions, and non-default values raise the chance of hallucinations and pronunciation errors, so audition the value you plan to ship. 0 remains the only value validated for production. For value-by-value guidance, see Expressivity and Configure the Voice Agent. Two new OpenAI LLM models Deepgram's managed OpenAI provider adds two models: Model Pricing Tier gpt-5.6-luna Standard gpt-5.6-terra Advanced { "agent": { "think": { "provider": { "type": "open\_ai", "model": "gpt-5.6-luna" } } } } For the full catalog, see LLM Models. ![Deepgram]() Deepgram Power enterprise voice solutions with Deepgram’s Speech-to-Text, Text-to-Speech, and Voice Agent APIs. Real-time, accurate, and built for scale. [View Deepgram →]() Sources [Original source]() [Read Expressivity for Flux TTS voices, and two new OpenAI models on Creators Toolbox]() --- Canonical source: https://creatorstoolbox.com/blog/deepgram-expressivity-for-flux-tts-voices-and-two-new-openai-models