The book of Revelation mentions harps two other times (Revelation 5:8; Revelation 14:2). In keeping with their usage in the Old Testament (1 Chronicles 13:8; 1 Chronicles 15:20, 1 Chronicles 15:28; 1 Chronicles 16:5; 1 Chronicles 25:1, 1 Chronicles 25:6), harps appear in Revelation to accompany singing of praises to God.
2 And I saw what appeared to be a sea of glass mingled with fire and also those who had conquered the beast and its image and the number of its name, standing beside the sea of glass with harps of God in their hands.