Graham, who grew up hearing her mother play Clair de lune on piano, keeps a “stack” of Debussy’s piano music on her own piano, music that she still plays to this day. “She introduced me to Impressionist art,” Graham says, “and she loved Impressionist music.” Debussy is still the mezzo’s favorite composer to play on the piano, keeping her in touch with the girl who “fantasized about the Eiffel Tower and going to Paris” while growing up in New Mexico.

Her connection with French music developed further when she began singing; once she started a career, her voice seemed suited to performing in that language. “The voice kind of makes that decision,” she says. “Mine has always had a rather slender quality, a rather lyrical quality, and I always had an easy top. That lent itself to the lyric French repertoire,” she explains. Instead of a “weighty” timbre that would work best in Verdi or Puccini’s operas, her voice is at its most comfortable in the songs and operas of Debussy, Berlioz and Fauré.

With the Chicago Symphony led by Pierre Boulez this weekend, she’ll sing Berlioz’s orchestral song cycle Les Nuits d’été (Summer Nights), six songs that joke about love, mourn its absence and offer other ineffable thoughts. “I just love the way that, especially in Les Nuits d’été, Berlioz plumbs this whole other world of expression,” she says. She recorded one of the finest versions of the songs on Sony in 1997, and still bubbles over with enthusiasm when talking about it now.

Are there any important moments in the orchestra she tries to keep track of? “Let me just go get my score!” she volunteers, to answer a question more complicated than it was meant to be. Laughing, she says that “there are always signposts that make me grin.” She finds one at the end of the first song (“Villanelle”), laughs a bit more, then lets us in on the joke: The narrator sings of returning fresh, wild strawberries home to his lover, and, it turns out, wild strawberries were once considered an aphrodisiac. Not everyone will catch it, but that association changes the way Graham sings the song.

“There’s a certain real, expressive drama in Berlioz’s music for me,” says Graham. “He was so influenced by Gluck, who was breaking out of the Classical restraint.” Berlioz’s biographer, David Cairns, amplifies that point, writing that Berlioz wrote “18th-century music with a 19th-century sound.” It advances the poise of Mozart’s era and adds a keyed-up expressiveness, and Graham knows just how to communicate it.

Graham sings of love when she sings with the CSO Thursday 31.