Horn died Thursday from complications of diabetes, The Hollywood Reporter said Friday.
A pianist since age 4, Horn started her own trio in 1954, The Reporter said.
She made her first recordings in the 1960s then decided to stay in Washington, raise a family and perform locally rather than pursue a national career.
She returned to the national scene in the 1980s when she began recording for Steeplechase and quickly achieved fame when she moved over to the Verve label in 1987, The Reporter said.
Horn's Verve recordings features such jazz luminaries as trumpeters Miles Davis, Wynton Marsalis and Roy Hargrove, saxophonists Joe Henderson and Gary Bartz and drummer Elvin Jones.
Her 1997 Miles Davis homage "I Remember Miles" won her a Grammy for best jazz vocal performance in 1998. She was nominated for nine Grammys in all.
Horn is survived by her husband, Sheppard Deering, and a daughter.