Authenticity in music- an impossibility?

Technology plays a huge part in today's society, but it has always played a part in music. Today it is impossible to create music that doesn't have roots in previous forms, and therefore near impossible to create something totally new. Using the three examples below I want to highlight this issue of originality in music.

http://www.youtube.com/watch?v=hRyDB4RWJdw

http://www.youtube.com/watch?v=25VGdNU3nrU

http://www.youtube.com/watch?v=6JBAxkZun3s

The first clip is a live performance by Ella Fitzgerald doing "Mack the Knife" in Berlin. In this clip she is doing a cover, but she forgets the words halfway through. Instead she begins skatting and the result is a completely new version of the song. It is indisputably brilliant, but is it authentic?

Second is a clip from Imogen Heap doing a live recording of her own song "Just for Now". In this clip she uses various recording instruments and computer functions to layer her own voice over a static track. While impressive, is this authentic? Or does the use of technology make her performance less impressive than Fitzgeralds?

Finally, the final clip is from GirlTalk. Girltalk's music has brought up many disputes over authenticity given that it is literally the combining of previously made songs to create a completely different song. Many would argue that this is inauthentic because he has not actually recorded his own song. Yet if you were to examine the majority of popular songs today you would be able to pick out several elements that have been adapted from previous musics and even directly 'borrowed' from other songs.

All three of these examples relate back to the evolution of music and the issues of authenticity that arise with trying to define what is 'real' music. I first started thinking about this when Kristina mentioned in class that she hadn't realized Elvis only produced covers. It is rare that when listening to a popular song one considers that it may not be the artists own work, yet in media, everything comes from something else. The point of this post however, isn't to answer all these questions of what is right and wrong, but to point out the endless debate over musical innovation over time. I'm interested to know what other people consider "real" or "authentic" in music and which, if any, of the three examples I listed would fall into those categories?