Each consists of seven basic notes, plus several variable notes used for ornamentation and modulation. Each is a certain modal variety subject to a course of development () that is determined by the pre-established order of sequences, and revolves around 365 central nuclear melodies known as (each of these melodies being a ), which musicians come to know through experience and absorption. This process of centonization is personal, and it is a tradition of great subtlety and depth. The full collection of in all is referred to as the "radif". During the meeting of "The Inter-governmental Committee for the Safeguarding of the Intangible Heritage" of the United Nations, held between 28 September – 2 October 2009 in Abu Dhabi, "radifs" were officially registered on the UNESCO List of the Intangible Cultural Heritage of Humanity.