At the age of 100, most people would be well into their retirement and simply looking forward to a quiet old age. But composer Elliott Carter plans to work faster than ever.

“Composing is the thing I enjoy most,” says the legend, who has had a major impact on modern classical music. “There’s nothing better than waking up in the morning and figuring out what I’m going to do that day, what I hope to accomplish, what kind of music I’d like to write. Or perhaps, I will try to solve some problem in music that made itself clear to me that evening.

“I used to enjoy writing it down,” he confides, “but now, I’m getting a little tired of that, so I instead try to find things I like in my head before I write them.”

Carter completes a single composition almost every week, one of the reasons for his prodigious output throughout his career. He’s composed more than 140 works—47 in the last 10 years and nine alone in 2007.

“An old man has no memory whatsoever, so I don’t have many pieces in my head,” Carter says in his self-deprecating manner. “I get stuck with whatever piece it is I’m working on and I become a fanatic. I just want to get it down and finish it. I never stop thinking about things in the piece and what to do with them. As I’m getting older, I’m getting more impatient and want to finish pieces soon.”

Most people get birthday presents wrapped up in fancy paper, but for his centenary on December 11, Carter is being honored with concerts around the world, including one at Carnegie Hall led by James Levine of the Boston Symphony Orchestra and Daniel Barenboim, pianist and former conductor of the Chicago Symphony Orchestra.

Levine and the Boston Symphony will introduce Carter’s Interventions for Piano and Orchestra, along with a program that includes Stravinsky’s The Rite of Spring. Barenboim will perform on the piano.

“Elliott is one of the most important composers of the last 50 years—it’s a physical phenomenon that after the age of 85, he developed a new style and I don’t even dare say it is a late style because he might find another one 20 years from now,” says Barenboim. “Many years from now, people will see his music as some of most important music written of our time.”