Dastgāh (Persian: دستگاه) is a musical modal system in traditional Persian art music. Persian art music consists of twelve principal musical modal systems or dastgāhs; in spite of 50 or more extant dastgāhs, theorists generally refer to a set of twelve principal ones. A dastgāh is a melody type that a performer uses as the basis of an improvised piece.
Each dastgāh consists of seven basic notes, plus several variable notes used for ornamentation and modulation. Each dastgāh is a certain modal variety subject to a course of development (sayr) that is determined by the pre-established order of sequences, and revolves around 365 central nuclear melodies known as gushehs (each of these melodies being a gusheh), 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 gushehs in all dastgāhs 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.
The dastgāh system has been a major influence in the maqam system in the Arabic music, both of which are deeply rooted in the Sassanid Persia's melodies, which entered into the Islamic world following the Arab conquest of Iran in the 7th century.
The system of twelve dastgāhs and gushehs has remained nearly the same as it was codified by the music masters of the nineteenth century, in particular Mîrzā Abdollāh Farāhāni (1843–1918). No new dastgāh or large gusheh has been devised since that codification. When in the modern times an āvāz or dastgāh has been developed, it has almost always been through borrowings from the extant dastgāhs and gushehs, rather than through unqualified invention. From this remarkable stability one may infer that the system must have achieved "canonical" status in Iran.
The term dastgāh has often been compared to the musical mode in Western musicology, but this is inaccurate. A dastgāh is usually the name of the initial mode of a piece, which the music returns to—and moreover, a dastgāh identifies a group of modes grouped according to tradition. In short, a dastgāh is both the collective title of a grouping of modes and the initial mode of each group.
According to musicians themselves, the etymology of the term dastgāh is associated with “the position (gāh) of the hand (dast) [on the neck of the instrument],” The Persian term dastgah can be translated as "system," and dastgāh is then "first and foremost a collection of discrete and heterogeneous elements organized into a hierarchy that is entirely coherent though nevertheless flexible."
In conventional classifications of Persian music, Abū ʿAṭā, Daštī, Afšārī, and Bayāt-e Tork are considered sub-classes of Šur dastgāh. Likewise, Bayāt-e Esfahān is a sub-class of Homāyun, reducing the number of principal dastgahs to a total of seven. A sub-class in the conventional system is referred to as āvāz.
The Seven Dastgahs
Most scholars divide the traditional Persian art music to seven Dastgahs, although some divide them to 12 Dastgahs (by counting Abu Ata, Dashti, Afshari, Bayat-e Kord and Bayat-e Esfahan as separate Dastgahs rather than subcategories of other Dastgahs). Those who categorize the traditional Persian art music into seven Dastgahs often also list 7 Avazes (Persian: آواز, which means songs) in conjunction with these Dastgahs. The following is a list of the 7 Dastgāhs and 7 āvāzes:
- Segāh ("third place")
- Čahārgāh  ("fourth place")
- Rāst-Panjgāh ("fifth place")
- Homāyun 
Note that in some cases the sub-classes (āvāzes) are counted as individual dastgāhs, yet this contradicts technicalities in Iranian music.
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- Bruno Nettl, The Radif of Persian Music: Studies of Structure and Cultural Context (Elephant & Cat, Champaign, 1987)
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- Persian music, Nowruz make it into UN heritage list, Press TV, 1 October 2009, .
- Nowruz became international, in Persian, BBC Persian, Wednesday, 30 September 2009, .
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