Let them play to him with drum and harp. Why does he take up drum and harp? So that not only his voice but his works may sing his praise. When one takes up a drum or harp, one’s hands agree with one’s voice. So you, too: if when you sing Alleluia, you also give bread to the hungry, or clothe the naked, or welcome the stranger, not only does your voice make sound, but your hands harmonize because your deeds harmonize with your words. You’ve taken up an instrument, and your fingers agree with your tongue.
But the mystery of drum and harp should not be passed over. On a drum the skin is stretched, and the strings are stretched on a harp. How well did Paul play on drum and harp when he said: “To me the world has been crucified, and I to the world” (Gal 6:14)! And Christ, who loves the new song, wishes you to take up a drum or a harp when he teaches you: “Whoever wishes to be my disciple, let him deny himself and take up his cross and follow me” (Mt 16:24). Let him not set aside his harp, let him not lay down his drum: Let him be stretched on the wood and let the lust of the flesh dry up. The more the strings are stretched, the higher the sound they make. So that the Apostle Paul’s harp might make a high sound, he said: “Forgetting what lies behind, stretching toward what lies ahead, I follow after toward the prize of a lofty call” (Ph 3:13-14). He stretched himself, Christ touched him, and the sweet truth was the sound he made. “On drum and harp let them play to him” (EnPs 149, 8; PL 37, 1953-1954).
Is this stretching things too far? Paul stretching himself, becoming a drum on which Christ plays? There’s another place where Augustine calls the cross a drum.