Sloane was associated with Second City for all but one of its 50 years. She held virtually every title in the place: associate producer, executive producer, founder of the e.t.c. second troupe, founder of the national touring company, co-founder of the Toronto branch of Second City, producer emeritus.
But those titles don't fully convey the import of a gifted woman who could spot raw talent with ease and who provided a crucial nurturing presence in what was, especially in the early years, almost exclusively a boys' club.
"In a business that is filled with heartbreak and rejection, she somehow could heal those wounds in a flash of a smile and restore confidence to keep us going," Jim Belushi, another comedian Sloane mentored, said Friday.
Other young comedians who started out at Second City in the 1960s, '70s and '80s testified to her maternal qualities.
"You loved Joyce, and you were afraid of her at the same time," former Second City cast member Stephen Colbert said Friday. "But she was incredibly kind to me and believed in me. For the first year, she called me Michael. When she started calling me Stephen, I knew I had made an impression."
Said Tina Fey from the set of television's "30 Rock": "She would be just as happy if you came out of Second City with 'a nice husband' instead of a movie career."
Tim Kazurinsky, another of Sloane's charges, said, "Everybody who comes to Second City has issues. She was the mother to the largest dysfunctional family in the world. Second City was like Marine boot camp, but over in this corner there was this little Jewish mother. It's hard to imagine the void."
Added actor George Wendt, who went on to TV fame in "Cheers": "She cared about every waitress and dishwasher, not just the famous alumni. If you got some good news or a gig or something, you called your mom and then you called Joyce. And if your mom had passed away, you called Joyce first."
And comedian Jeff Garlin said, "The one consistent thing that happened to me at Second City was that Joyce believed in me and always let me know I was the funniest person there. Whatever else happened."
It was Sloane who held Radner's hand whenever things got tough, onstage and off. "When Gilda came out on stage," Sloane told the Chicago Tribune in 1999, "the whole audience wanted to put its arms around her."
At the time, Sloane still could not speak of Radner, who had died of ovarian cancer a decade before, without her voice breaking.
It was also Sloane who headed out to the College of DuPage in suburban Chicago and found a raw, edgy young student named John Belushi and hired him in the early 1970s without even requiring him to audition.
"Oh, John," Sloane used to say, her round face lighting up with the memory of one of her most notable discoveries.
But the Belushis were hardly the only ones. Sloane also trekked to London, Ontario, in 1990 to check out a young comic named Nia Vardalos. Sloane brought her to Chicago, and Vardalos went on to make "My Big Fat Greek Wedding."
Sloane was den mother to Chicago actors, comedians and improvisers for nearly a half century; she regarded the likes of Vardalos, Fey, Bonnie Hunt and countless others as her surrogate daughters.
Sloane remained a fixture at the theater in recent years, despite her age and declining health.
"The loss," said Andrew Alexander, the executive producer of Second City, "is monumental."
Sloane, who was born in June 1930, is survived by her daughter, Cheryl; a grandson; and a brother, Danny Coval.
A California memorial service is planned for 7 p.m. March 1 at the El Portal Theatre, 5269 Lankershim Blvd., North Hollywood.