Anyone who subscribes to the New York Review of Books should have a look at Stephen Greenblatt's piece, "The Lonely Gods." Here's the beginning of the article from the NYRB site:
When James Levine’s tangled halo of white hair was picked up by the spotlight shining down over the orchestra pit at the May 9 performance of Die Walküre, at the Metropolitan Opera in New York, the audience roared with pleasure and relief. With good reason. Levine’s bad back and other health woes had forced him to pull out of multiple events he was scheduled to conduct, including one recent performance of this opera, the second in the Ring cycle. But there were no signs of diminished vigor or control on that evening.
Greenblatt eventually gets to something important regarding the visions of divine power and human freedom as found in Paradise Lost and Die Walkure, but the full article is behind a paywall. Thanks to Jutta I have a print-out and will be happy to share. Here's a comment on it from a listserv. By all means have a look, especially if you happened to catch the recent Met Opera performance of Wagner's opera.