Gregorian chant is the ancient, traditional music of the Western Church, with roots in the Jewish liturgy at the time of Christ. It is essentially liturgical music, as the music fits around the words rather than the other way round. The singer of Gregorian chant therefore truly conforms to St Augustine's famous adage: “he who sings prays twice”. The Second Vatican Council commended the continued use of Gregorian chant, urging that “... other things being equal, it should be given pride of place in liturgical services” (Sacrosanctum Concilium,116).
Useful guidance on the singing of chant and on the pronunciation of liturgical Latin can be found in the Parish Book of Chant published by the Church Music Association of America, and which is issued to members of the Ealing Abbey Plainchant Choir (EALPC). An online version is available at https://media.musicasacra.com/books/pbc_2nd.pdf
There are numerous resources on the Internet dealing with the history, development and use of chant, and with musicological aspects. They include the following:
Dom Daniel Saulnier, Gregorian Chant, A Guide
Arlene Oost-Zinner and Jeffrey Tucker, An Idiot's Guide to Square Notes
Many other resources can be found at http://musicasacra.com/resource-lists/
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