Her voice is warm and burnished with compassion on radio and TV voiceover spots for a health care provider, possibly the most melodic soft-sell ever.
Then there's her real craft. Consider, for instance, her sharp, take-no-prisoners delivery as C.J. Gregg in "The West Wing," and her manic chatter as a blowsy woman in the indie film "The Way Way Back."
Or enjoy the sly purr she employs as Bonnie, a wayward but good-hearted parent and grandparent who's trying to stay reformed in the new CBS sitcom "Mom" (9:30 p.m. Monday).
Anna Faris co-stars as her similarly imperfect daughter.
"It's acting," Janney said. "I feel like actors like to be challenged and play all different types of roles. For whatever reason, I've been given the opportunity to do so."
Her talent has been on display on Broadway, where she earned Tony nominations for "9 to 5" and "A View from the Bridge," and in movies including "American Beauty" and "Drop Dead Gorgeous."
She earned four Emmy Awards for playing White House press secretary C.J. Cregg in "The West Wing."
In person, the willowy Janney is polite and soft-spoken -- the product, the Ohio native says, of her proper Midwestern upbringing.
Her 6-foot height, she says, earned her some brutal early career assessments from short-sighted agents: One said her roles would be limited to a handful of options, including aliens.
And Janney acknowledges that her 1999-2006 experience on the intricate, densely scripted political drama from Aaron Sorkin ("The Social Network," HBO's "The Newsroom") was something she treasures but also acutely recalls as demanding.
A multicamera comedy like "Mom" offers a different experience, with shorter rehearsal days followed by a Friday taping.
"This is so civilized," she said, both for her and for Faris, "who has a baby and can see her child grow up."
But it's laughs that Janney really is after.
"Comedy is what I love the best. I'm just drawn to it," she said, with Carol Burnett and Mary Tyler Moore among her TV favorites as a youngster.
"Physical comedy, sweet poignant moments, heartbreaking scenes, classic straight man, you name it," she said.
"Mom" airs at 9:30 p.m. Mondays on CBS.
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