The up-and-coming stars sat in a circle at Motown headquarters, staring in disbelief at the stylish woman who was lecturing them like a small, chic drill sergeant.

"Do not confuse me with your mother," she told the Supremes, the Temptations, the Marvelettes, Smokey Robinson and the Miracles, and other luminaries-to-be. "She's stuck with you and I'm not."

Berry Gordy Jr., who founded the Detroit music label in 1959, had decided his young diamonds-in-the-rough required some polishing, and Maxine Powell — former model, actress and proprietor of a top local modeling school — was just the person to do it.

From 1964 to 1969, Powell ran Motown's in-house "charm school," a mandatory course of instruction in proper sitting, standing, eating, dressing, chatting with fans, responding to reporters and every other act of public deportment that might make or break a Motown star.

"There were a million things I taught them, especially stage technique," Powell reminisced to People magazine in 1986. "You never turn your back on the audience. You walk a straight line when you cross the stage. You do not hold the mike so close and open your mouth so wide it looks like you're going to swallow it."

"Why do you make those faces?" Powell asked the young Diana Ross, who tended to emote as she sang.

"I'm feeling the song," Ross told her. "I'm souling."

"Go home and 'soul,' and knock yourself out in front of the mirror so you can see how unpleasant you look," Powell snapped.

Powell, who was credited with instilling discipline and evoking confidence in some of pop music's biggest names, died Monday at a hospital in Southfield, Mich. She was 98.

Powell, who was divorced, has no immediate survivors, friends said.

But half a century after her Motown days, she had plenty of admirers.

Powell "showed me that there was the possibility of beauty, grace, integrity and meaning to my life," Ross said in a statement.

In an interview with The Times, Martha Reeves, the lead singer for Martha and the Vandellas, said Powell "personified grace, style and character, and I did my best to imitate her."

While serving on the Detroit City Council from 2005 to 2009, Reeves hired her former teacher, then in her 90s, to speak at convalescent homes and schools. Powell also gave personal development classes at Wayne County Community College.

"She taught motivation," Reeves said of the woman she called a friend and mentor. "She taught how to walk, talk and be socially acceptable."

Powell made her points in a distinctive style that was fondly recalled in a statement by her Motown boss Gordy.

"Ladies, remember your gloves, walk with class like you were taught — and always remember, do not protrude the buttocks," Gordy wrote in Powell's precise manner. "One day you will perform for the kings and queens of Europe, but for now we must make the best of it on the circuit of the chit-ter-ling" –- the chitlin circuit being those venues where blacks could perform in segregated America.

Born Maxine Blair in Texarkana, Texas, on May 30, 1915, Powell grew up in Chicago with an aunt who taught etiquette classes. After studying dance and acting, she modeled and worked as a manicurist. In 1948, she moved to then-booming Detroit and three years later opened what was thought to be the city's first black modeling agency.

Berry's sisters were among her clients, and Berry's printing business produced circulars for her fashion shows. Soon Berry asked her to see his entertainers and critique how they carried themselves.

While the artists were coached by others at Motown in voice and dance, they were Powell's for two hours daily.