Basic-Unity-Head-Rotation | humanoid head in Unity | Animation library

I would like to rotate a head of a humanoid character given x, y, z rotation values using a script (without using any other object in the scene as "look" direction).

When setting-up the rigging of a Humanoid character (humanoid prefab --> Rig --> Animation Type: Humanoid --> Configure --> Muscles & Settings), you see the following interface: https://docs.unity3d.com/Manual/MuscleDefinitions.html

In this menu, under Head, you can drag a slider to move e.g. your humanoid head up and down. I want to achieve the same with a script, but I don't know how to do this.

This question never received a proper answer with example code: https://answers.unity.com/questions/824628/can-we-using-script-to-moving-the-muscles-in-unity.html

I presume I have to do something with HumanPose.muscles (https://docs.unity3d.com/ScriptReference/HumanPose-muscles.html), however with the lack of code samples, I have no idea how to approach this.

Edit 3: This link has a code sample for HumanPose, but I didn't get it to work yet: https://forum.unity.com/threads/humanposehandler.430354/

How to get the head muscles of a humanoid character and rotate them by giving values through a script? (Or any other way how to rotate the head using head rotation values, without another object in the scene). Any help would be appreciated.

I receive a JSON formatted message from which I extract the radian values and change it into degrees: