“If we did anything in the name of John Coltrane, of course she was the person we went to and asked for assistance and advice,” said Mr. Hines, a former artistic director at Trane Stop. “If there were any musicians that we wanted to present, she was the major person we would go to first.”

Carla Washington, the Clef Club’s community engagement manager, called Ms. Alexander a repository of historical and cultural knowledge. “She knew the music; she knew the musicians; she had stories to tell in reference to the music,” Ms. Washington said. “She dedicated her life to the music of jazz .”

Mary Alice Elizabeth Lyerly was born on July 23, 1927, in High Point, N.C., to Goler and Bettie (Blair) Lyerly . Both she and John Coltrane were only children, born just 10 months apart, and they grew up together in the house of their maternal grandparents.

They often played and took dancing lessons together, and even received a common musical education from Coltrane’s father, John Sr., who sang and played violin in the house. In a 1962 interview, Coltrane described Ms. Alexander as “like a sister to me.”

No immediate family members survive. Ms. Alexander’s husband, Billy Alexander, died in 1995.

She moved to Philadelphia with her mother in 1944, a year after Coltrane did. Eight years later, Coltrane, who had served in World War II, used a G.I. Bill loan to buy a house across from scenic Fairmount Park. Ms. Alexander moved in, along with her mother and Coltrane’s mother, Alice (Blair) Coltrane. Ms. Alexander lived there until 2004; after a severe stroke left her without the ability to speak, she spent her final years at the Watermark nursing home.

Mr. Pope, who studied with Coltrane as a teenager , remembered Ms. Alexander as having a deep spiritual connection to jazz.

“The music, in her mind, was the motor to the soul,” he said. “She used to preach all the time: It’s our responsibility to create a platform for the young people, pass it on down to them. And eventually out of that platform, the younger generations can continue to pass it on.”