Gosh, how'd I miss this all these years...!
It's a lot of work being a Daniel Johnston fan!
By the way, For Mac users, you can save the youtube video to your computer in Safari by going up to the menu and selecting "activity" under "window." Then scroll down, find the file that's streaming, hold down the option key, and double click the mouse. That will save the file to your desktop, at which point you can extract the audio using any number of programs.