Say() and googleTTS - how to change pitch and speaking rate from a rule?

I’m late to the party but just found out how to get chromecast audio sinks and GoogleTTS to actually work on the OH 3.1 installation. With SSML I can choose and change the voice ‘on the fly’ but what I didn’t find after reading through related posts here for hours is any way to set a different pitch or speakingRate for a say-ing.
I know about Settings/Other Services/…, what I search is a way to change those params by code.
I see them cached as plain text for every single saying in /var/lib/openhab/cache/org.openhab.voice.googletts just like the text itself so it well looks like they are transmitted every time the tts is called.

Has anyone found a way to achieve this?

To answer myself:

Apparently not the way I had thought. But! Google supports SSML and there is prosody

"<speak><prosody rate=\"fast\" pitch=\"+2st\">Hey, the request to update the timetable has been sent already. </prosody> <prosody rate=\"slow\" pitch=\"-1st\"> That may take a few seconds though</prosody> </speak>"