It was under the pastorate of Msgr. Hickey that, in 1934, Theodore Marier began fifty years of musical service at St. Paul's, first as organist and then from 1947 as choir director. A graduate of Boston College, he was director of band and music there from 1934 to 1942. In 1940 he received a master's degree from Harvard, and over the course of the years he was also choir director or lecturer at Emmanuel College, Newton College of the Sacred Heart, and Boston University.
As Marier was taking over the choir, Mgsr. Hickey was inspired by the papal encyclical Mediator Dei to encourage congregational participation--quite unusual in a time when the choir or altar boys gave all the responses. It was Marier's experience that the Gregorian Chant was ideally suited both to congregational singing and for musical nourishment. Gradually, the parish developed the habit of singing the Ordinary of the Mass (Kyrie, Gloria, Credo, Sanctus, Agnus Dei). In 1958, the Vatican's Instruction on Sacred Music and Sacred Liturgy continued the directive that every parish should have a boys choir but especially encouraged that "every effort must be made that the faithful of the entire world know how to give the responses in chant."
The St. Paul's Choir School began in 1963 with twenty-five students chosen from throughout the archdiocese. Under the direction of Theodore Marier, the young musicians sang in the parish choir with members of the Harvard Catholic Club. Harvard students also helped out with the recreation program. The school was designed as a four-year course for students of academic ability and musical talent, assigning two periods of each school day to music, plus an hour after school. The music program included sight reading, tone placement, appreciation, theory and history, and instrumental studies.
The first years of what was relabeled the Boston Archdiocesan Choir School were extraordinary. The choir made guest appearances with the Boston Symphony Orchestra at Symphony Hall and at Tanglewood, with the Boston Philharmonia, and with the Handel & Haydn Society. Annually they performed with the Boston Ballet in the Nutcracker Ballet, with Arthur Fiedler conducting.