And even the earliest of these writings document new concepts of musical structure that would ultimately underpin the emergence of the radif-dastgah tradition. Early writings about music associated with the Qajar court describe idiosyncratic models of procedural musical structure. They alternately referred to twelve dastgah or four shadd, which might also be called dastgah. But in both cases writings described a unique, separate procedure of musical development that defined each shadd or dastgah. There was not one shared superstructure unifying the organization of all dastgah: each one required a separate explanation of how it worked, from the beginning of a performance to the very end. While authors initially described varying numbers and terminology for these performance-based structures, seven dastgah eventually become a common framework for this procedural concept of musical structure. Descriptions of seven dastgah suggest the musical procedures of each dastgah could relate specifically to how instruments were played. Following this logic, a text dated 1912 from an observer named Mirza Shafi Khan described the melodic progression of seven different dastgah in terms of different tunings for strings and changing hand positions over the duration of a performance. This referred to how the music could be played on the tar (tār), a specific long-necked, fretted lute.
However many dastgah there were in the early to mid-nineteenth century, musicians took the seven dastgah of the late nineteenth century and made changes to this particular tradition in the twentieth century. It is the seven dastgah of the late Qajar court and their transformation in the twentieth century that define the radif-dastgah tradition as musicologists understand it today. Even musicians with the most direct connections to the earliest practitioners of the seven dastgah in the nineteenth century were engaged in a music tradition steeped in modern musical change.
The centerpiece of the radif-dastgah tradition as musicians and scholars discuss it today is the radif: a specific collection of monophonic melodic material that provides the structure for the tradition’s theory, pedagogy, and performance practice. The melodic material of the radif ranges from short motivic fragments to melodies with longer multisectional development, yet all of these different musical pieces and motives have come to be referred to individually as gusheh. The modern radif and current Iranian music theory subdivides the gusheh of the radif into twelve or thirteen subdivisions: subsets of gusheh that are thought to have modal affinity with one another. The primary term for these subsets of gusheh is dastgah, though smaller subsets of gusheh may be referred to as dastgah or avaz. Seven dastgah comprised the original designated structures of the tradition, with smaller avaz-dastgah being designated somewhat later in the twentieth century. Currently musicians vary in their distinction between the original seven and the additional four to five avaz-dastgah. Some treat the original seven dastgah as primary and the avaz-dastgah as secondary and this is often where the question of how many avaz-dastgah exist depends on the particular radif or performer. Others make no distinction between the original seven and the additional, smaller avaz subdivisions, typically referring to all of them equally as twelve dastgah.