Many critics and musicians consider his last few decades a case of arrested development. In his recent memoir, "Hallelujah Junction," composer John Adams describes Glass' style as "largely unchanged over a period of nearly 40 years . . . in general I have had the feeling that he rarely troubles himself much with delving into new possibilities or combinations for the many different instruments that he writes for."
The main event is the Glass Ensemble playing the score to "Koyaanisqatsi" alongside the film -- something the group has done, by Glass' estimate, 200 times. Glass, who plays keyboards with his ensemble, has written new parts for the Los Angeles Philharmonic, which will presumably thicken the music's textures.
Working on that project for experimental documentarian Reggio highlighted for Glass the difference between an independent and studio film.
"The earlier you start on a film, the closer you'll be aligned -- you can form a relationship around the artistic goals," he says. "With independent films there's often more time, because often the funding isn't in place."
With "Koyaanisqatsi" -- the name means "life out of balance" in Hopi -- Glass had more than two years to work on the score. "There was no one waiting for the film -- there was no distributor! So we were left alone to make a film -- which I realized later was a great luxury."
Today Glass is struck by how pertinent the film seems, at a time when its notions of the world's interconnectedness and the runaway power of technology have gone mainstream. But the film's identity has changed since its premiere in 1982.
"When we first showed it," he says, "people thought it was a head trip. People seriously thought you had to get high before you watched it. It wasn't too long, only four or five years, for people to realize there was actually a movie."
His opera in L.A.?
The other major Glass work that he'll be performing at the Bowl is the brief "Spaceships" scene from "Einstein." It's a reminder that the celebrated opera itself -- one of the most important and groundbreaking American operas in history -- has never been performed in Los Angeles. But Glass himself is warily optimistic.
"We have real interested parties, and Wilson has gone back and done some new drawings. A lot of the groundwork has been laid. We're getting close to that again -- but we're in a moment when nobody has any money. If we don't get to L.A. this time, I give up."
The plight of "Einstein" shows something that might surprise laymen: Despite Glass' fame and accomplishments, he still has trouble getting work staged.
His new opera on the life of 16th- and 17th-century German astronomer Johannes Kepler is scheduled to premiere in Linz, Austria, in September with no plans for a U.S. staging.
The future for his opera about Walt Disney is unclear, especially in the composer's and animator's native land. The opera was commissioned by New York City Opera, and is still in development but with the departure of then-incoming general director Gérard Mortier, it has no clear home.
"America's a funny place," Glass said. "It's not impossible that the perfect American opera might not be put on here. Disney is the quintessential American story. I'm not slamming Disney at all" -- as some have claimed -- but trying to offer "a very complex view of a genius, on how someone's vision could be so powerful that it could be known around the entire world."
In some ways, then, doing any big-scale artistic endeavor is a little like working in Hollywood -- the combination of logistics, timing, ego, commerce and artistry.
"It didn't surprise me," Glass says of the roadblocks and frustrations he's run into across his career. After all, he said, art fills a need that's intangible and often unrequested.
"It's always a struggle," he said. "It's like your aunts and uncles say: 'Don't complain, nobody asked you to do it.' "