Ten experts decide who and what changed the course of music history.

The Reformation fundamentally changed everything. There is musical life before and musical life after the Reformation, and in England the shift was most dramatic. All the clerical books and the Catholic rite that was needed to perform the gorgeous pre-Reformation polyphonic music was swept away, all in one year. From 1549, everything was replaced by a single slimline book that contained all you needed to practise a far simpler version of Christian worship.

The Book of Common Prayer was now in English and it swept away the large mass settings and the morning offices of matins and lauds. They were combined into one single matins service. The great evening offices of vespers and compline, again, were combined to create what we know as Evensong. Interestingly, the composers of the day were given absolutely no manual on what to do about it. All they had was the prayer book. You could no longer hear something as grand as Thomas Tallis’s Gaude Gloriosa or any of the great pre-Reformation works, the latest was marked 1548. As soon as policy changed, that music was no longer appropriate.

Tallis pretty much single-handedly...