You can thump your chest and rattle --> that's what wild animals (a gorilla and a rattlesnake) do to impress/scare off opponents
Stand in front of your piano --> try to look distinguished/impressive (perhaps posing for a photo).
Appartently Mr Richards is trying to save his own position (which is a messenger pigeon left behind when the camp moved on --> mr Richards has lost support and back-up now that the (political) situation has changed).
I had some thoughts on the following lines: