If there is such a thing anymore as a certifiable celebrity composer, Philip Glass is it. This, his 75th birthday year, has been a big one for him, with his 9th Symphony premiering in New York, a 10th on the way, a tour with the Kronos Quartet revisiting his 1999 Dracula score, his opera Kepler premiering at the Sottile Theatre for the Festival, work on an opera about Walt Disney proceeding apace for a January premiere, and slobbering retrospectives of his five decades of making boundary-busting music all over the place.

The doors to the Dock Street Theatre remained closed until just 10 minutes before the scheduled 5 p.m. start time for Saturday’s third Music in Time presentation, at which the prolific minimalist workhorse was slated to be fawned over by host John Kennedy. Eager enthusiasts ranging in age from the single digits to the high doubles milled about in an increasingly packed lobby while they swapped fanboy stories about Glass’ enormous, and enormously influential, body of work, a good deal of which has been presented and even premiered at the Festival, going back to his Hydrogen Jukebox in 1990.

The program, which was only announced a few minutes before the show, noted only a snippet from one of his very earliest pieces, 1981’s Glassworks. But the 75-minute program managed to shoehorn in a solo piano work performed by Conor Hanick (“Opening” from Glassworks), as well as an impromptu dashing-off by the composer himself of a short segment entitled “Wichita Vortex,” from Hydrogen Jukebox, played to a recording of Alan Ginsberg reading his original poetry for the piece, which had only been secured moments before the program began. Glass nailed it, naturally, even without sheet music, knocking off the piece as casually as if it were something he did first thing every morning. When the seven young members of the Spoleto Symphony Orchestra launched into the “Closing” of his Glassworks at the end of the program, with Glass sitting on the stage with them and watching, you could practically smell the animal fear leaking out of their pores. They did a fine job, and nobody had a nervous breakdown. Professionals, through and through.

In between the music, Kennedy mostly listened as Glass talked at length on a range of subjects:

On writing operas about Great Men (e.g. Kepler, Einstein, Galileo, Gandhi, etc.): “When a great man dies, it becomes a global event. Of course the death itself is ordinary, as all deaths are. But it becomes an event. It’s like watching a sunset; you can’t stop watching.”

On America: “I’ve traveled a lot, all over the world. Our culture is so intense and complex. Very few people in Europe or Asia understand the complexities we deal with and what we are capable of as a people.”

On changing what music and opera was understood to be: “In the ‘70s we wanted to make a radical change in music and opera, in what operas were about. We wanted to change the modality, to get rid of narrative as it was understood. I realized the chronology of the story didn’t matter. It’s like looking at a scrapbook of photos — you don’t really care what order the photos are in.”

On Samuel Beckett: “I was working on a piece of Beckett’s called Company, and I sent him a note asking him, ‘Where does the music go?’ He replied, ‘In the interstices of the work, as it were.’ I didn’t bother asking any more after that.”

On Johannes Kepler: “He was a really mean guy. But he was also an extraordinary guy.”

On his love of science: “It’s sometimes said that science is the art of measuring the world. I like that. Science has in a way come full circle recently. Before science, there was just imagination. Aristotle tried to understand the world by imagining it. And then science gave us this process of measurement and understanding. And now look at things like string theory — that’s an incredible act of imagination.”

On his inadequacy as a young scientist: “I was never good at math. Arithmetic, maybe, but not math. If you can count to eight in a lot of different ways, you can write Einstein on the Beach…I feel like I was a failed astronomer.”

On working: “A really good day for me is eight to 10 hours of writing music. Eight is normal. Eleven is just too much.”

On collaboration: “I owe everything to my collaborators. For me, that’s the engine of change. Lots of people talk about how important it is for artists to find their voice, but what you really want to do is lose your voice. That’s how you evolve and grow as an artist. Only when I encounter the unknown can I change my own language.”

Bonus trivia! Philip Glass is the first cousin once removed of Ira Glass, host of the nationally syndicated radio show This American Life, the sacrificial altar upon which monologist Mike Daisey a few weeks ago had his heart publicly torn from his living body over “inaccuracies” in his monologue The Agony and the Ecstasy of Steve Jobs, which had aired on This American Life in January and which (in the opinion of some, including Ira Glass) torpedoed the entire institution of journalism before opening at the festival last week. Ask Philip Glass about it — it’ll be fun!