Sonia Leon Gilbert, 89, an opera singer and lifelong champion of multicultural understanding who was raised in a Jewish household and became a founder-president of the Philadelphia-based Bawa Muhaiyaddeen Fellowship and Mosque, died of a rare cancer Friday, Aug. 24, at her Merion home. She was surrounded by family and friends.

Born and raised in Philadelphia, Ms. Gilbert, a lover of music and beauty, enjoyed an early career as an opera singer but also went on to make professional contributions in radio, publishing, and film. She was a decades-long student and supporter of Sufism, a mystical branch of Islam.

Through her many endeavors, Ms. Gilbert was above all a humanitarian and an advocate for mutual respect and harmony among diverse populations of people.

"Sonia was such a mother and mentor to so many groups of people internationally," said Nahid Angha, cofounder and codirector of the International Association of Sufism. "Her loss is huge, and now I am at a loss for words because they do not have meaning in a case such as this."

Ms. Gilbert was a proud graduate of Overbrook High School and the Curtis Institute of Music, winning admission in an audition before violinist and Curtis director Efrem Zimbalist Sr. and institute founder Mary Louise Curtis Bok. The daughter of Max M. Leon, founder of the Philadelphia Pops Orchestra, Ms. Gilbert made her operatic debut at 19 in a concert with Metropolitan Opera star Robert Merrill and the Philadelphia Pops at the Academy of Music.

In music, as in much else in her life, Ms. Gilbert defied limits.

"She always embraced the great, the good, the beautiful, the wise," said daughter Wynne Alexander, a civil rights author and Philadelphia resident.

In the 1950s, Ms. Gilbert performed live on radio, singing popular music and operatic arias.  As a radio producer in the 1970s, she mixed classical music recording with rhythm and blues, rock, and gospel. In the years in between, she performed in occasional concert venues and raised her five children.

Ms. Gilbert was also involved in publishing, including the Lapidary Journal, an international magazine on gems, rocks, and mineralogy, from 1986 to 1998.

In the 1970s, she began her Sufi education with Sheik M. R. Bawa Muhaiyaddeen, studying with him both in Philadelphia and in his native Sri Lanka. It blossomed into a life's work of fostering interfaith relationships among Muslims, Christians, and Jews around the world. The Bawa Mahaiyaddeen Fellowship she helped found is based in the city's Wynnefield section but has branches throughout the United States, as well as chapters in Sri Lanka, Australia, England, and Canada.

Her concern for the spiritual and socio-political environment also led to her partnership in One Light Pictures, a company involved in documentary film production that coproduced the PBS Cuban photographic history REVOLUC!ON: Five Visions.

Ms. Gilbert was the first recipient of the international Sufism organization's Inspiration Award. She was a frequent speaker at international Sufism symposiums and wrote or appeared in numerous articles in the Sufism Journal.

In addition to daughter Ms. Alexander, Ms. Gilbert is survived by her children Robert Klein, Beth Sheard, Leif Owen Klein, and Mignon Groch, her sister Ruth Weiman, seven grandchildren and three great-grandchildren.

Services will be Sunday, Aug. 26,  at 11 a.m. outside the Bawa Muhaiyaddeen Fellowship and Mosque, at 5820 Overbrook Ave., Philadelphia, and at 1 p.m. in the chapel of Roosevelt Memorial Park, 2701 Old Lincoln Highway, Trevose, Pa. All are welcome.

In lieu of flowers, the family requests contributions be made to the fellowship at 5820 Overbrook Ave., Philadelphia, Pa. 19131.