The Secret Weapon of the Reformation

Alexandra Walsham, "The godly and popular culture," in John Coffey and Paul C.H. Lim, ed., The Cambridge Companion to Puritanism, pp. 288, 291:

The power and popularity of psalm-singing also deserves more than passing notice. Once described as 'the secret weapon of the Reformation', the capacity of congregational singing to delight and inflame the heart cannot be discounted.22 A common accompaniment to fasts and journeys to Sunday and weekly sermons, it too fostered identity and solidarity in ways that had the potential to draw people magnetically into the select band of saints.

22. D. MacCulloch, The Later Reformation in England, 1547-1603 (2nd edn, Basingstoke, 2001), p. 138.

Dairmaid MacCulloch, The Later Reformation in England, 1547-1603 (2001 ed.), p. 138:

One secret weapon of the English Reformation was music: the metrical psalm.

Also, see D. MacCulloch, The Reformation: A History (2004 ed.), pp. 33, 312, 593; and D. MacCulloch, Thomas Cranmer: A Life (1998 ed.), p. 618.