Back when I wrote my big book, I argued in Chapter 18 (“Problem Area II: The Role of the Choir”), in footnote 23 on page 388, that is can be acceptable to have non-Catholics and non-believers in a Catholic choir when the Catholic community has decided that it values the presence of such singers for the sake of its common worship. I was channeling Fr. Aidan Kavanagh OSB, my thesis advisor at Yale, who said more than once to me that the choir had an essentially musical role and hence one should admit members on the basis of musical ability. “It is notoriously difficult to establish … boundaries,” I pointed out. I advocated for flexibility and openness, even as I argued that the choir has a liturgical role.
Then I was on the drafting committee for the US bishops’ document Sing to the Lord: Music in Divine Worship (2007), and the issue came up again and went in a different direction. The final document emphasized at nos. 49-50 (excerpted below) that liturgical musicians are disciples and belong to the assembly of the baptized faithful.
What do you think? The issue is shot through with lots of complication, and application of any principles will require sensitivity. There are reasons why various congregations might come up with different answers to the question, depending on the way in which congregations understand their musical ministry. Is it notoriously difficult to establish boundaries? What should they be? How should they be applied?
49. Liturgical musicians are first of all disciples, and only then are they ministers. Joined to Christ through the Sacraments of Initiation, musicians belong to the assembly of the baptized faithful; they are worshipers above all else. Like other baptized members of the assembly, pastoral musicians need to hear the Gospel, experience conversion, profess faith in Christ, and so proclaim the praise of God. Thus, musicians who serve the Church at prayer are not merely employees or volunteers. They are ministers who share the faith, serve the community, and express the love of God and neighbor through music.
50. All pastoral musicians—professional or volunteer, full-time or part-time, director or choir member, cantor or instrumentalist—exercise a genuine liturgical ministry. [See Sacrosanctum Conciliium, no. 29]