This episode is special, as it is not about programming concepts in general, but about how to add sound to a processing.js program. You won't miss any important programming concepts if you skip it.
Any libraries you import in the standard version of Processing are not available in Processing.js, so we need to think of another approach to play sound files.
We will edit the file template.html using a text editor. One new line will instruct the web page to load the audio library. Other lines will make the sound files ready for use.
The files from this episode can be found at: https://github.com/hamoid/Fun-Programming/tree/master/processing/06/e141_pjs_audio
Note: in the Examples menu of Processing there are some processing.js programs that include audio, but they did not work on my computer.