Book excerpt: An interesting and readable book about the master musicians of the medieval Islamic world.Taking as its subject the world of medieval Islamic music, Three Master Musicians deals with the three men who led artistic life in Abbasid Baghdad in the 9th century. Two of these men were Ibrahim al-Mawsili and his son Ishaq who were musicians to caliphs and aristocrats and kept the equivalent of a latter day academy of music. The third man featured in Dr. Caswell's new book is Ibrahim ibn al-Mahdi - a remarkable musician for his time. He was the son of a caliph and the uncle of several caliphs (and he himself held the caliphate of Baghdad for a brief spell being known as the Black Caliph due to his colour). Ibrahim ibn al-Mahdi was a wonderful musician with a formidable vocal range who popularised singing and is said to have created the 'modern' mode of Arabic singing.Three Master Musicians is an in-depth look at the medieval music makers who changed Arabic music forever.