Devoti Musica Cordis (Pious Music of the Heart)
Johann Heermann (1585–1647) published his Devoti Musica Cordis (Leipzig/Breslau, 1630) at the height of the Thirty Years War, when his Silesian parish of Köben was repeatedly sacked and he himself suffered severe illness that ended his preaching ministry. The collection's centrepiece, 'O Gott, du frommer Gott' — called his 'Master Song' — moves through the complete arc of a day's needs from waking to sleep, encompassing godly labour, patient suffering under affliction, and preparation for holy dying. Its combination of earthy practicality and eschatological hope made it an ideal devotional text for Protestant families facing the destruction of the war years. The hymn was subsequently incorporated into major Lutheran hymnals and set by Johann Sebastian Bach.