For instance, many gusheh actually exist in more than one dastgah with only small amounts of modal transposition or rhythmic variation, such as kereshmeh in the daramad. On another level, all of the dastgah tend to share gusheh that perform a certain function or behave in a certain way. For instance, highly rhythmic gusheh often appear in performance without much alteration, while gusheh with less metered construction are more likely to be improvised upon. Some gusheh are considered central to any performance of a specific dastgah, while others are considered less central and performers have the option of including them in their proper place within the dastgah or excluding them altogether.
A majority of gusheh in the radif derive from three concepts that define three possible melodic sections. One central concept is the idea of singing poetry using only its poetic foot as the rhythmic basis of its melody (she‛r). Another is the concept of tahrir, with is a specific style of vocal improvisation without any words. Additionally, the concept of forud is often folded in with poetry and tahrir. A gusheh may use different combinations of tahrir and poetry, with the forud appearing at the end as a cadential figure. Conversely, forud can also be classified as independent gusheh in and of themselves, as can a single phrase of poetry or tahrir. Using these different types of melodic sections in different combinations can give gusheh a variety of melodic forms throughout the radif, but only a small number of gusheh do not employ them at all. The gusheh that fit this pattern are stylistically vocal, since they take a majority of their organization from poetry and ideas surrounding vocal performance. The emphasis on poetic meter over and above musical meter in many gusheh is key to the overall performance aesthetic. Poetic meter provides most of the rhythmic organization of this type of gusheh, which embodies an approach to rhythm that is ostensibly unmetered in a musical sense, meaning a drum does not accompany the melodies of these gusheh. Their loose, poetry-driven rhythmic structures also relate to using relatively small ensembles. They favor using one main soloist at any given moment in a performance, who makes choices about improvisation that a few additional instruments are able to follow and imitate.
Most of the gusheh that are not derived from poetry, tahrir, or forud belong to a separate category of gusheh that utilizes two different metered forms intended for performance by instruments only: the reng (reng), which is a group instrumental piece in a moderate 6/8-style rhythm, and the chahar mezrab (chahār meżrāb), a virtuosic solo instrumental piece usually played in a fast 2/4. In contrast to the stylistically vocal gusheh, these two forms employ a distinct, steady melodic pulse often punctuated by a drum. In the course of performing a particular dastgah or avaz-dastgah, instruments play all types of gusheh, regardless of their stylistic orientations toward vocal or instrumental characteristics. By contrast, if a vocalist is present he or she would only participate in performing stylistically vocal gusheh and not the instrumental gusheh.
Gusheh and Dastgah in Persian Music: Classic Framework and Modern Interpretations
