The practice of liturgy in the Christian church as a whole ranges from the utterly simple to the incredibly complex. From the simplest [spoken only, no music at all], it progresses through spoken with sung hymns; spoken with intoned psalms and sung hymns; chiefly spoken with some parts intoned by the officiating priest and psalm and hymns sung by congregation; Chanted liturgy; full sung Mass.
However, having tracked down your source, this book refers to the complex changes that took place at the Reformation in England. Previously, the church was Roman Catholic, in which music played an important and vigorous role. One of the factors that led to change was a revulsion against the sung liturgy [which was in Latin, and so not understood by the general populace], and an attempt to make all priests/ministers abandon the use of music.
Vinnicomb, who was an Abbot, clearly tried to fund a foundation in his [college/monastery/abbey] to encourage and train boys who would form a part of a choir.
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