As a girl she lived for five years in Morocco before returning to the United States to attend the Juilliard School's pre-college program, where she studied the violin, piano, singing, theory, and composition.
She attended Sarah Lawrence College, where she earned a bachelor's degree in music composition in 1967.
She continued with graduate studies at Columbia University (MA 1969), and, as a pupil of John Corigliano, at the Manhattan School of Music (DMA 1984).
Wallach is also known for her symphonic work The Tiger's Tail which won the National Orchestral Association composition contest in 1991 and for her chamber opera The King's Twelve Moons.
Her secular oratorio, Toward a Time of Renewal for 200 voices and orchestra was commissioned by the New York Choral Society for their 35th Anniversary Season at Carnegie Hall.