'Harp' in the Bible

Even inanimate things that produce sounds—whether flute or harp—if they don’t make a distinction in the notes, how will what is played on the flute or harp be recognized?

When He took the scroll, the four living creatures and the 24 elders fell down before the Lamb. Each one had a harp and gold bowls filled with incense, which are the prayers of the saints.