Adjusting the sound of nanoTTS

I have some difficulty to understand the voice on nanoTTS which is too dull in French. It seems it is the same as on picoTTS, anyway it’s not better.
I think there is a possibility to adjust the sound on nanoTTS. But is this applicable in Rhasspy and how?

Okay. Now I switched for Google Cloud TTS which is perfect.

Meanwhile I wanted to try Larynx. And just for information, this has freezed my system completely!