create-app.js
Say verb:
voice-server.js
Say verb will use the voice defined in the textToSpeech object. In this case, the voice used is “aura-asteria-en”.
If you want to overwrite the voice the Say verb uses, you can pass the voice attribute to the say method. Here is an example:
voice-server.js
say method will use the “aura-asteria-en” voice, and the second say method will use the “aura-luna-en” voice. The voice attribute is optional. If you don’t pass it, the Say verb will use the voice defined in the application configuration.