Indeed, scholars classify gusheh that do not conform to the modal parameters of their given dastgah as modulatory figures, thus giving their noncompliance with the modal parameters of the dastgah a modal function in the course of performance. Yet tension remains between the specificity and idiosyncrasy of melodic material within the seven dastgah and the framework of abstract modality that many musicians and scholars like to use to describe the dastgah.
The development of more composition within the radif-dastgah tradition facilitated greater exploration and development of dastgah modality. The reng and the chahar mezrab became models for composition, focusing notions of composition on instrumental forms. A new instrumental form also appeared in the course of dastgah performance called pish-daramad (pīshdarāmad). Though the pish-daramad is listed in the earliest available charts of the gusheh, musicians of the twentieth century regarded it as a separate phenomenon that was added later, distinct from the other instrumental gusheh. Like the reng and chahar mezrab, the pish-daramad has both a specific rhythmic count and a specific place in the order of performance. It was played by all instruments in the performance in a moderate 2/4. It was designed to precede the daramad as a kind of overture, thus the name pish-daramad (before-daramad). The expanding application of composition within a largely improvisational performance practice allowed greater exploration of the concept of dastgah modality, as musicians made decisions about the modal parameters they would use to compose a piece that was not defined by any particular sequencing of gusheh or poetic structure.
In addition to the instrumental compositions, the insertion of metered songs (taṣnīf) into larger dastgah performances gave musicians and poets alike an opportunity to create contemporary compositions. While the vocal gusheh consistently used classical Persian poetry, tasnif could use newly composed melody and text. The tasnif would ultimately become the largest realm of composition. Its placement in the performance of a dastgah presented an opening for changes to performance structure. Tasnif provided moments of metered singing in the middle of a dastgah performance, in the midst of long sections of vocal improvisation. Any and all instruments could also perform tasnif in full heterophony with the voice, as meter allowed for full melodic coordination of an instrumental ensemble with the singer.
Gusheh and Dastgah in Persian Music: Classic Framework and Modern Interpretations
