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 are the melodic units used by Ottoman classical music?
makam

Hydrogen, as atomic H, is the most abundant chemical element in the universe, making up 75% of normal matter by mass and over 90% by number of atoms (most of the mass of the universe, however, is not in the form of chemical-element type matter, but rather is postulated to occur as yet-undetected forms of mass such as dark matter and dark energy). This element is found in great abundance in stars and gas giant planets. Molecular clouds of H2 are associated with star formation. Hydrogen plays a vital role in powering stars through the proton-proton reaction and the CNO cycle nuclear fusion.
What 2 forms of mass is most of the universe consisted of?
dark matter and dark energy

A distinct Greek political identity re-emerged in the 11th century in educated circles and became more forceful after the fall of Constantinople to the Crusaders of the Fourth Crusade in 1204, so that when the empire was revived in 1261, it became in many ways a Greek national state. That new notion of nationhood engendered a deep interest in the classical past culminating in the ideas of the Neoplatonist philosopher Gemistus Pletho, who abandoned Christianity. However, it was the combination of Orthodox Christianity with a specifically Greek identity that shaped the Greeks' notion of themselves in the empire's twilight years. The interest in the Classical Greek heritage was complemented by a renewed emphasis on Greek Orthodox identity, which was reinforced in the late Medieval and Ottoman Greeks' links with their fellow Orthodox Christians in the Russian Empire. These were further strengthened following the fall of the Empire of Trebizond in 1461, after which and until the second Russo-Turkish War of 1828-29 hundreds of thousands of Pontic Greeks fled or migrated from the Pontic Alps and Armenian Highlands to southern Russia and the Russian South Caucasus (see also Greeks in Russia, Greeks in Armenia, Greeks in Georgia, and Caucasian Greeks).
When did the nation reestablish itself ?
empire was revived in 1261