CHICAGO — Cleotha Staples, one of the founding members of the renowned Chicago soul and gospel group the Staple Singers, died Wednesday at the age of 78.

She had been suffering from Alzheimer’s disease for 12 years, and had been under 24-hour home care. Her longtime caretaker was with her when she died at 11:11 a.m. Wednesday in her high-rise condominium on the South Side, according to her sister, Mavis Staples.

Cleotha Staples was a vital component of the Staple Singers’ distinctive harmonies. Her soprano voice, which rang out like a bell and descended with a distinctive twang, was among the key musical elements in the family group that sold tens of millions of records and scored hits such as “I’ll Take You There,” “Respect Yourself” and “Uncloudy Day.”

Cleotha Staples was the first child born to Roebuck “Pops” Staples and his wife, Osceola, in 1934, on a sharecroppers farm near Drew, Miss. A little more than a year later, Pops Staples moved to Chicago, where he found work at the Chicago stockyards and later sent for his family. In the South, Pops Staples grew up with blues guitarists such as Charlie Patton and sang in gospel groups. When he moved north, he gave up music for a time as he worked to support his family, which eventually also included Pervis, Yvonne and Mavis, all of whom were born in the 1930s (a fourth daughter, Cynthia, was born in 1952).

In the late ’40s, Pops Staples began teaching his children the songs he had learned singing with his family at Dockery Farm plantation in Mississippi. Soon after, the group became proficient enough that they were invited to perform at churches on the South Side. By 1953, the Staple Singers were cutting records and began touring outside Chicago.