Etta James, whose powerful, versatile and emotionally direct voice could enliven the raunchiest blues as well as the subtlest love songs, most indelibly in her signature hit, “At Last,” died on Friday morning in Riverside, Calif. She was 73.

Her manager, Lupe De Leon, said that the cause was complications of leukemia. Ms. James, who died at Riverside Community Hospital, had been undergoing treatment for some time for a number of conditions, including leukemia and dementia. She also lived in Riverside.

Ms. James was not easy to pigeonhole. She is most often referred to as a rhythm and blues singer, and that is how she made her name in the 1950s with records like “Good Rockin’ Daddy.” She is in both the Rock and Roll Hall of Fame and the Blues Hall of Fame.

She was also comfortable, and convincing, singing pop standards, as she did in 1961 with “At Last,” which was written in 1941 and originally recorded by Glenn Miller’s orchestra. And among her four Grammy Awards (including a lifetime-achievement honor in 2003) was one for best jazz vocal performance, which she won in 1995 for the album “Mystery Lady: Songs of Billie Holiday.”