The description says: “Besides the robotic voices offered by Microsoft Windows, this program also allows you to use natural voices (Alloy, Echo, Fable, Onyx, Nova, Shimmer) provided through the OpenAI API. Additionally, the program supports the Replicate API, which offers some sample voices and voice cloning.”
How do you access them? When I switch to OpenAI API, the button below the text to read, switches to “Send”. I enter text, select a voice, click Send, and get the message “Please enter you OpenAI credentials”. The Microsoft voices might be ok in rare cases, like adding a computer voice in a sci-fi video or song. Program is easy to use. Help on Vovsoft website never describes how to use these other APIs.