'Harp' in the Bible

It is similar for lifeless things that make a sound, like a flute or harp. Unless they make a distinction in the notes, how can what is played on the flute or harp be understood?

and when he had taken the scroll, the four living creatures and the twenty-four elders threw themselves to the ground before the Lamb. Each of them had a harp and golden bowls full of incense (which are the prayers of the saints).