Armstrong became the fourth director of the St. Olaf Choir in 1990,[1] continuing the tradition begun by the choir's founder F. Melius Christiansen in 1911, sustained and developed by his son, Olaf Christiansen, and strengthened and enhanced by Kenneth Jennings.

Anton was born in New York City on April 26, 1956, to William Benfield Armstrong (1916–2002) and Esther Louise Holder (1917–2007).

Armstrong grew up on Long Island where he and his mother were active singers in a local church choir.

[2] Armstrong was invited to conduct the Masterwork Festival Chorus's performance of Robert Ray's Gospel Mass at Carnegie Hall on March 18, 2019.

[4] In March 2024, Armstrong was the guest conductor for the Manassas Chorale's annual "Voices United" concert.