S1 and Voxtral Mini TTS are available through the OpenRouter API, so switching between them takes a model slug change rather than a new integration.
S1, from fish-audio, is priced at $15/M UTF-8 bytes on OpenRouter.
Voxtral Mini TTS, from Mistral AI, has a 4,096-token context window and is priced at $16/M characters on OpenRouter.