Joshuah Bearman says:
The guy peruses god knowsh how many clips of songs, historical performances, homemade bedroom noodling, high school band recitals, and low budget YouTube instrumental instructional videos, and combines them to form his own songs. The result is seven diverse — and good! — songs of various genres. That first one arranges some fairly active and original funk out of dozens of different instruments and melodies, including a guy with a mullet playing a theremin.
UPDATE: Joel posted this on Gadgets on March 4.
I Know it is a Bold Declaration, But The YouTube Mash-Up Just Took a Step Toward Art