The individual pieces, gusheh-ha, are not performed literally according to any of the versions given above. Each gusheh is merely a framework. A good performer is expected to fill in the framework, or to elaborate upon the melodic material of the radif, and to do this extemporaneously. Thus, between the radif and a performance is a set of processes forming a separate layer of music theory, which may be designated the "theory of practice." Its counterpart in Western music would be included in composition, but since the composition of Persian music is extemporaneous, this subject may best be labeled "improvisation."
Iranian musicians do not isolate this branch of theory, and they do not teach it formally. In fact, in the literature improvisation is hardly mentioned except for some of the more practical problems, such as realization of the ornaments from Western notation. Indeed, most of the theory of practice comes to an Iranian intuitively. Because music in Iran is still mainly taught by rote (with the aid of printed instruction books), the student simply absorbs the compositional procedures without being aware of them as such. For this reason, a musician is often unable to explain precisely what he is doing during his improvisation. Likewise, Persian music theorists, considering this aspect of music to be an intuitive procedure, do not discuss it in their writings. Therefore, in contrast to the branches of Persian music theory that have been well developed and extensively discussed (the size of the microintervals, for instance), the foreign musicologist has little indigenous methodology or terminology on which to base a study öf improvisation.
A further obstacle in this area is the readily apparent discrepancy between the theory of practice and the practice of practice. Not infrequently, after a lengthy interview regarding performance practices, a performer will illustrate the aspects of practice he has just described by playing something entirely different from what he has just said ought to be played. One must realize from the beginning that in Persian music there is no "always," for no rule or custom is inviolable. It is highly unrealistic, therefore, to make any statement about practice without qualifying it with terms such as "generally," "usually," "the typical," or "frequently."
The study of improvisation attempts to get beneath what is intuitive or natural in the musician's performance and by generalizing from many performances, to discover the ordering principles of the performance. For this purpose, the extemporaneous composition of Persian music may be analyzed as a series of decisions. After deciding on the dastgah he will play, the performer must decide which gusheh-ha of that dastgah he will perform, and in what order he will play them. Then there are numerous decisions relating to how each gusheh is to be composed. These include the elaboration and extension of the basic model to create a piece and the joining of several pieces to form that movement of the dastgah performance called the gusheh.
Persian Classic Music: The Dastgah Shur
