As was alluded to in the comments there, most of the loss was probably due to stretching and demagnetization of the two tapes. Generational loss would most likely consist of horizontal scanline offset (due to time base skew) and horizontal blurring, though eventually the time may get off far enough to cause some of the other artifacts seen in that video.

so: prior art?!

It's his take on Alvin Lucier's famous "I Am Sitting in a Room":

http://www.youtube.com/watch?v=Jfssj80oNuM

The original recording is linked from the Mashable article.