Tts-ultimate choosing voice

I am very happy with the results of the node-red-contrib-tts-ultimate.
I got it working in no time. In my test flow I use it to simply convert a text to audio, play it directly in the browser and make the file available for download.

My question is regarding the chosen voice (using google cloud TTS):
Is there a way I can change the voice by means of a message?
How does the command msg have to look like?

I tried this: msg.voice = "sv-SE sv-SE-Standard-D - MALE";
..without any success.

Any hints?
Could this be done by means of SSML? What is the syntax of SSML in this node? I did not get this work properly either yet.

Thx for any pointers!