If you are a NewscasterVocalizer PRO user and you Upgraded to NewscasterVocalizer Agency can add voice customization by adding SSML Tags/Codes inside there Script Text file.
Speech Synthesis Markup Language or SSML allow for more customization in your audio response by providing details on pauses, and audio formatting for acronyms, dates, times, abbreviations, or text that should be censored.
You will find the SSML code examples on AWS Knowledge-base here: https://docs.aws.amazon.com/polly/latest/dg/supported-ssml.html
You can use the examples on this page and modify them according to your need in the speech. Then add that modified text in your scripts to customize your speech.
To give you an example how it works here is a shot example of SSML markup:
Here are <say-as interpret-as="characters">SSML</say-as> samples.
I can pause <break time="3s"/>.
I can speak in cardinals. Your number is <say-as interpret-as="cardinal">10</say-as>.
Or I can speak in ordinals. You are <say-as interpret-as="ordinal">10</say-as> in line.
Or I can even speak in digits. The digits for ten are <say-as interpret-as="characters">10</say-as>.
I can also substitute phrases, like the <sub alias="World Wide Web Consortium">W3C</sub>.
Copy this code and past it on notepad. Save it as .txt format and create a speech file using this .txt file.
You will get a speech file like the attached speech file.
Note: You must have both NewscasterVocalizer PRO and NewscasterVocalizer Agency in your account.