 But during the Islamic era the musical box was enlarged, a fourth string was added, and the base for the tuning pegs (Bunjuk) or pegbox was added.In the first centuries of (pre-Islamic) Arabian civilisation, the oud had four courses (one string per course — double-strings came later), tuned in successive fourths.Curt Sachs said they were called (from lowest to highest pitch) "bamm", "maṭlaṭ", "maṭnā" and "zīr".