When she was nine, her family moved to Bolivia. For the next decade, her talent in music, particularly on the piano, grew rapidly. She returned to the United States to study piano at Bennington College, and took instruction in composition from Louis Calabro and Henry Brant. She studied composition with Otto Luening, Jack Beeson, and Vladimir Ussachevsky at Columbia, where she earned a doctorate in 1968.
The following year, she helped found the New York-based Da Capo Chamber Players and served as the group's pianist. She also took on a faculty post in composition at Bard College in 1972 and has remained there in that capacity. Tower wrote a number of successful works for the Da Capo Players over the years, including Platinum Spirals (1976), Amazon I (1977), and Wings (1981). The group received several awards in its early years, including a 1973 Naumberg Award. Up to the 1980s, all of Tower's works were scored for solo instruments or chamber ensembles. Her first orchestral composition, Sequoia, came at the relatively late date in her career of 1981. It was an immense success, and was taken up by many American and foreign orchestras.
Buoyed by her first effort, Tower began writing more works for orchestra in the 1980s, and left the Da Capo Players in 1984. The following year, she became composer-in-residence for the St. Louis Symphony Orchestra, holding that post until 1988. On a commission from the Milwaukee Ballet, Tower wrote Stepping Stones in 1993. The composer conducted a performance of Celebration, an excerpt from the ballet, at the White House. Among her compositions from this period are the 1996 Rapids (Piano Concerto No. 2), which she wrote for her friend, the pianist Ursula Oppens; and Tambor (1998), written for the Pittsburgh Symphony Orchestra. Beginning with the 1999-2000 season, Tower launched a three-year stint as composer-in-residence with the Orchestra of St. Luke's. In 2005 she accepted a commission for a work, Made in America, to be played by 65 community orchestras spread across all 50 American states. The piece was played by all the orchestras in their 2005-2006 seasons, and its recording by Leonard Slatkin and the Nashville Symphony won three 2008 Grammy awards, in the fields of Best Classical Album, Best Orchestral Performance, and Best Classical Contemporary Composition. Tower lives in Annandale-on-Hudson, New York.