The Harp as a Christian Symbol represents music, instruments, joy and worship in praising God.
Ps. 71:22 I will praise you with the harp for your faithfulness, O my God; I will sing praise to you with the lyre, O Holy One of Israel.
The harp is also recognized as an attribute of King David as told in I Chronicles 13:8:
And David and all Israel played before God with all their might, and with singing, and with harps, and with psalteries, and with timbrels, and with cymbals, and with trumpets.
The Easton Bible Dictionary provides the following definition, meaning and emblem for the Harp Christian Symbol in the Bible.
(Heb. kinnor), the national instrument of the Hebrews. It was invented by Jubal (Gen. 4:21). Some think the word _kinnor_ denotes the whole class of stringed instruments. It was used as an accompaniment to songs of cheerfulness as well as of praise to God (Gen. 31:27; 1 Sam. 16:23; 2 Chr. 20:28; Ps. 33:2; 137:2).
In Solomon's time harps were made of almug-trees (1 Kings 10:11, 12). In 1 Chr. 15:21 mention is made of "harps on the Sheminith;" Revised Version, "harps set to the Sheminith;" better perhaps "harps of eight strings."
The soothing effect of the music of the harp is referred to 1 Sam. 16:16, 23; 18:10; 19:9. The church in heaven is represented as celebrating the triumphs of the Redeemer "harping with their harps" (Rev. 14:2).