Marianne Challis, a cabaret singer and Broadway voice teacher, died of natural causes on Aug. 29 in Manhattan. She was 58.

Challis primarily taught Broadway theater professionals. She also served as a vocal technician for organizations such as Disney Prods. and Lincoln Center for the Performing Arts. She was an associate professor of vocal studies at the U. of Hartford’s Hartt School in Connecticut and served as a consultant to its musical theater program.

Also in Connecticut, Challis and her husband, Frank Root, operated Broadway Boot Camp, a workshop for young actors and musical theater performers through their Southport Studio Theater program.

Her recent cabaret shows included performances at Feinstein’s at the Regency and the Laurie Beechman Theater in New York City. She recently won a Bistro Award for outstanding female vocalist from Backstage.

She released a live CD, “Confessions of a Middle-Aged Party Girl” in 2006.

Challis graduated from Eastern Illinois U. with a degree in vocal performance and music education. She also studied with the opera department at Northwestern U. and at the Guthrie Theater in Minneapolis.

She began her professional life in musical theater, performing in summer stock and at many of the tristate area’s major musical houses. In her 20s, Challis toured the country in the Hermione Gingold production of “Side by Side by Sondheim.”

Her final theater performances were starring as Nellie Forbush in the New York City Opera production of “South Pacific.”

Challis is survived by Frank Root, her husband of 30 years and a Broadway performer and director-choreographer; son Lonnie, a professional cellist; daughter Abby, an actress and singer; her sister; and their 97-year-old father.

Donations may be made to the Marianne Challis Scholarship Fund for Musical Theater, Southport Studio Theater, 1305 Jennings Road, Fairfield, CT 06824, or Broadway Cares/ Equity Fights AIDS: Marianne Challis, 165 West 46th St., Suite 1300, New York, NY 10036.