One of the most important features of Radif as the Iranian music repertoire is the consecutive modulations (modulation chains). Because of that, it needed to have changing notes. Hence, Dastgah as a fundamental concept of this kind of music, has the function that can organize this interrelations between the components of Dastgah, named Gusheh. In this article, it tries to search for the roots of these modulations and finding the probable reasons of the changing notes in Dastgah-e Mahoor from MirzaAbdollah-version. There has not been any obvious explanation in this field in the previous published references yet, and there are just some general and qualitative theories. While with regarding to the basic scale of Dastgah-e Mahoor as the first step and specification the unattached notes, it can be determinate the notes that are prone to change. Unattached notes has defined as the notes that have no fourth or fifth interval with other scale notes. This is the Owen Wright's definition about determinate of consonance ratio but in this article, it seen that, a complimentary definition, e.g. semi-unattached notes could explain the mentioned notes more accurately and in the functionality manner. On the other hand, the presence of dissonance factors can exert principals to not to violate some conditions in composing melodies. In this discussion, the perfect fourth interval has a pivotal role. It is not only as a criteria for melodic intervals but is used as important interval for defining unattached or semi-unattached notes and finally for any changing notes. The other dissonance factors are about the sequence and presence of melodic interval in the Tetrachord. There are three main intervals, named "Tanini", "Mojannab" and "Baghieh". Safieddin was the first one theorized the arrangements of these intervals for formation of consonance Tetrachords. Definitely, they were for more smooth and beautiful composing. Therefore, they could have utilized in arbitrary or non-arbitrary manner, as criteria in making the melodies including Radif-s gushe-s. In fact, it assumed that the Safieddin's rules, before the formation of the Radif-s could function.
Initially the fourth intervals between the notes of scale of Mahoor checked. It understood that the fourth and seventh notes have not this interval between each other. There for, it expected that the first changing notes are these ones. The important tip was that the dissonance factors were not for imposing a special manner but they were for avoiding of the errors or unpleasant combination of notes. There for, you can justify some Gushe-s like "Shekaste" and etcetera. The complicating matter was the transfer from one mode to another one that because of resolving the dissonance. In other words, more than its work as modulation, they are for resolving the dissonance factors.
In end with regard to all of these matters, some other factors must be considering for analyses, e.g. practicable register of the instrument of Tar, condition of the changing notes and condition of expression. For example some changing notes, because of their register, cannot be play in their right octave or it's necessary to consider the changing notes in cadence condition.