Read this: Ottoman classical music was an important part of the education of the Ottoman elite, a number of the Ottoman sultans were accomplished musicians and composers themselves, such as Selim III, whose compositions are often still performed today. Ottoman classical music arose largely from a confluence of Byzantine music, Armenian music, Arabic music, and Persian music. Compositionally, it is organised around rhythmic units called usul, which are somewhat similar to meter in Western music, and melodic units called makam, which bear some resemblance to Western musical modes.

What rhythmic units does Ottoman classical music use?
What is the answer? (If it cannot be answered, return "unanswerable")
units called usul