It all started approximately three decades ago with a Rice Krispies box and a toothbrush.

American cellist Alisa Weilerstein, who appears as soloist in Samuel Barber’s Cello Concerto on Dec. 7-12 with the Chicago Symphony Orchestra, was 2½ years old and home with the chicken pox. Her parents — pianist Vivian Hornik Weilerstein and Donald Weilerstein, founding first violin of the Cleveland Quartet — were away for performances, and Weilerstein’s grandmother was on baby-sitting duty. She devised toy instruments out of whatever was at hand, and Alisa happily thumped away on a cello crafted from a Rice Krispies box and a toothbrush. Despite her father’s worries about starting lessons too early, Alisa was playing on a real, if miniature, cello by age 4. A year later, she had learned by heart solo parts of major cello concertos.

Since then Weilerstein has forged a distinguished international career, performing on some of the finest cellos ever made, including a 1723 Montagnana. In 2011, the Chicago-based MacArthur Foundation awarded her a “genius” grant, citing her “impassioned musicianship” and “emotionally resonant performances of both traditional and contemporary music.”

Alisa Weilerstein feels a responsibility “to create the 21st century repertoire that will be inspiring for future generations.” | Photo: BBC Proms

In recent years, CSO audiences have heard Weilerstein in both types of repertoire. Since her CSO debut in 2009 in the Dvorak Cello Concerto, she has performed concertos by Haydn, Prokofiev and Elgar with the orchestra. In the 2015-16 season, she gave the world premiere performance of Outscape, a concerto commissioned by the CSO from French composer Pascal Dusapin. The Chicago Tribune called the piece “absorbing and important” and Weilerstein’s performance “the kind of debut most composers can only dream of achieving.”

“I like variety,” said Weilerstein, in a recent phone interview from Minneapolis, where her husband, Venezuelan conductor Rafael Payare, was guest conductor with the Minnesota Orchestra. It was a welcome chance for Weilerstein and Payare, and their 19-month daughter, Ariadna, to be in the same city at the same time. “I enjoy getting to wear different hats in a way. It keeps me curious and learning; one time period can influence and inform the other.”

Weilerstein cites another, more practical reason for performing both standard and more contemporary repertoire. “The cello repertoire is really small, especially pre-20th century,” she said. “It’s great, but compared with the violin or piano [concerto] repertoire, it’s really very, very limited.”

Furthermore, today’s new music can, potentially, become tomorrow’s standard repertoire. “I take [Mstislav] Rostropovich as my example,” Weilerstein said, referring to the legendary Russian cellist, who befriended and commissioned works by his era’s leading composers. “He is largely responsible for the incredible [cello] output in the 20th century of these amazing composers. Shostakovich is the most famous example, but also Benjamin Britten, Henri Dutilleux, Witold Lutosławski, György Ligeti; Rostropovich was their muse.

“I can happily say a lot of cellists of my generation also feel that way, and we feel a responsibility to create the 21st century repertoire that will be great and inspiring for future generations. And also, for our own benefit. That’s why I like to know what’s going on with composers of my own time and help create a cello repertoire that really might last.”

Musicians often revel in the joy of being able to discuss nitty-gritty performance details with living composers. Unlike Beethoven and Mozart, they are alive and able to describe exactly how to phrase the melodic line in bar 32 of their string quartet’s opening movement. But waiting for composers to finish a new piece can be excruciating.

“You have to have a lot of patience,” Weilerstein said. “There’s one composer I won’t name because I don’t want to put more pressure on him. I’m thinking if it takes until 2045, I’ll wait for [his cello concerto] because I think he’s really, really great. The Matthias Pintscher concerto I did, which I think is really wonderful, I premiered it in Boston this past March; it took him eight years to write it. I was gratified to see that the Dutilleux concerto [Tout un monde lointain], which is close to being a 20th century classic, was actually commissioned in 1960 and wasn’t premiered until 1970.

“When I did the revised version of Osvaldo Golijov’s Azul, which is a big concerto for cello, accordion and percussion players, it was 36 hours before the premiere that I got the final version. This is an age-old problem with composers, taking a long time.”

It took a long time for Weilerstein to realize that she had won a $500,000 MacArthur grant in 2011. The foundation sent her several emails, which, in her assured, no-nonsense way, she dismissed as spam. She also ignored their calls, but finally decided to answer the phone.

“It was a complete surprise,” she said. “I actually didn’t even know what it was. I was in Jerusalem at [pianist] Elena Bashkirova’s Jerusalem International Chamber Music Festival. After three or four calls, I figured maybe I should see what this is about. I kind of steeled myself; ‘OK, this is going to be a scam. They’re going to ask me for some password.’ ”

Weilerstein and her family are currently based in Berlin, and since 2008, she has been active as a spokesperson for the Juvenile Diabetes Research Foundation. She was diagnosed at age 9, and her regular regimen includes checking her blood sugar level up to 10 times a day.

“I started speaking out about research for a cure because I wanted to prove that as a Type 1 diabetic I could sustain the schedule anyone else could,” Weilerstein said. “Once I thought I’d proved that, I was kind of itching to speak out about it.

“It’s a royal pain,” she admitted, “but I generally approach it in a very practical way. OK, this has happened. I’m going to fix it and do something about it and that’s it. Living with Type 1 diabetes is a full-time job in itself. But it’s also completely possible with the right attitude and vigilance to live a really, really happy, productive and fun life.

VIDEO: Alisa Weilerstein in an iPhone video, discusses the Barber Cello Concerto: