ivr say: tts-voice

For IVR, how do I amend the text to speech tts voice tts-voice that "say" uses in Greet Long? In other words, how do I configure Flite within FusionPBX, (or file system if no GUI) ?

Currently it uses a thick male voice presumably from open tts flite.

say:press 0 for reception

The sparse documentation refers to say_gender, but with no specifics on how to configure it or separate the parameters from content...

https://docs.fusionpbx.com/en/latest/dialplan/dialplan_application.html?highlight=say

<module_name>[:<lang>] <say_type> <say_method> [<say_gender>] <text>

Advanced.. Modules, Say specifies English - enabled and Flite - enabled.

This file specifies callie for cepstral, which is not what say uses.

Code:
languages/en/en.xml:    <language name="en" say-module="en" sound-prefix="$${sounds_dir}/en/us/callie" tts-engine="cepstral" tts-voice="callie">
Demo IVR specifies ivr_menus/demo_ivr.xml tts-voice="rms". Robot-Mean-Square? About what he sounds like!

Can anyone point to a substantive guide on this?