Unlike the commercial audio CDs of the lectures the recordings here have the chat before and after the lecture which is fun.

My favourite lecture is the standalone "The Principle of Least Action" at

https://www.feynmanlectures.caltech.edu/II_19.html

Audio: https://www.feynmanlectures.caltech.edu/II_19.html#Ch19-audi...

This one is my favorite too. I had the three volumes of hardcover copy.

> Later chapters do not depend on the material of this special lecture—which is intended to be for “entertainment”

We might say this is the most important chapter in the whole series.