" Sing and make music in your heart to the Lord” (Eph. 5:19).94 The new song is sung first in the heart. It cannot be sung at all in any other way. The heart sings because it is filled with Christ. That is why all singing in the congregation is a spiritual thing. Devotion to the Word, incorporation into the community, great humility, and much discipline—these are the prerequisites of all singing together. Wherever the heart does not join in the singing, there is only the dreadful muddle of human self-praise. Wherever the singing is not to the Lord, it is singing to the honor of the self or the music, and the new song becomes a song to idols. "
― Dietrich Bonhoeffer , Life Together and Prayerbook of the Bible (Dietrich Bonhoeffer Works, Vol 5)