A system is a set or group of connected components which follow a specific goal so, in such a way that they construct a complex unit. Any system is made up of smaller systems, and a part of a larger system. In Persian, system is also called Dastgâh, such as the blood circulation system or the digestive system of the human body, in which a set of connected components circulate blood or digest food.

Considering the concept of a system, once can say that Radif is an organized set of 12 systems called five Âvâzes and seven Dastgâh-s, each of which comprised of smaller systems called Gusheh. Dastgâh-s are more comprehensive than Âvâz-s, i.e. Dastgâh-s have more complex systems than Âvâz systems.

Considering the importance of poetry in Persian culture and therefore its influence on music and singing poems in the form of Âvâz, it can be deduced that organizing classical Persian music began with collecting Gusheh-s in the form of Âvâz-s, and gradually, with the increase in the number of Âvâz-s, they were put in larger sets, forming Dastgâh-s. The term Dastgâh implies its comprehensiveness.

In this regard, Ruhollah Khaleqi writes: “Today, the style of categorizing Âvâz-s is very different from the past. Today the large Âvâz-s are called Dastgâh, and Persian music is usually said to be made up of seven Dastgâh-s, namely Mahur, Homayun, Shur, Se-Gâh, Châhâr-Gâh, Râst Va Panjgâh and Navâ.” (A Look at Music, Ruhollah Khaleqi)

Therefore, Persian music Radif has been compiles in five Âvâz-s, namely Âvâz-e Bayât-e Tork, Âvâz-e Abu-Ata, Âvâz-e Afshâri, Âvâz-e Dashti and Âvâz-e Bayât-e Isfahan, as well as seven Dastgâh-s, namely Shur, Mahur, Homâyun, Châhâr-Gâh, Se-Gâh, Navâ and Râst Va Panj-Gâh.

It must be reminded that the numbers 5 and 7, and their sum 12 are among mythical numbers, inspired by religious beliefs. Examples include the five books of Nezami (the 6th century poet), called the Nezami Pentadthe seven books of Rumi (the 7th century poet) called Masnavi; the ‘poetic’ seven seas; the seven firmaments; the 12 Shiite Imams, the five holy figures of Islam; 12 months of the year, the seven continents of the world and the five oceans, 12 hours of the day and night each. It has always been possible to create other sets under the title of a new Âvâz or a new Dastgâh.