The term translated harp
denotes a small string instrument held in the hand and plucked to make sound. This is the instrument the Levites used in their worship in the temple (Psalm 33:2; Psalm 71:22; Psalm 98:5; 1 Chronicles 25:1, 1 Chronicles 25:6).
8 And when he had taken the scroll, the four living creatures and the twenty-four elders fell down before the Lamb, each holding a harp, and golden bowls full of incense, which are the prayers of the saints.