Born in Lebanon, Ohio and educated at Smith College and Columbia University, she lived for many years in Italy, and even after her return to the United States in the early 1970s spent her summers in Verdi's hometown of Busseto where she continued her exhaustive research into his life.
The latter was an analysis of the modern opera business which she characterized as "monstropera", contrasting what she felt was its dehumanized, bourgeois approach with its past as a flamboyant yet more human spectacle.
During this time, Phillips-Matz was also general manager, fund-raiser, and public relations director for Menotti's Festival dei Due Mondi in Spoleto.
Her last major work was her biography of Giacomo Puccini, published in 2002, although she continued to lecture and in 2005 wrote the text for a book commemorating the 50th anniversary of the Washington National Opera.
Phillips-Matz died at her home in Manhattan, near Verdi Square shortly before her 87th birthday[2][3] In addition to the following books and her articles for Opera News, Phillips-Matz also wrote regular program notes for London's Royal Opera House,[3] essays in The Cambridge Companion to Verdi and The Puccini Companion, and feature articles for Playbill.