Persian traditional music relies on both improvisation and composition, and is based on a series of modal scales and tunes which must be memorized. The common repertoire consists of more than two hundred short melodic movements called Gusheh, which are classified into twelve Avāz-s, and finally these twelveAvāz-s are categorized into seven Dastgāh-s or “modes” called Shur, Mahur, Homayoun, Nava, Segah, Chahargah and Rast Panjgah. Each gusheh and dastgah has an individual name. This whole body is called the Radif of which there are several versions, each in accordance to the teachings of a particular master or Ostad. A typical performance consists of the following elements pīshdarāmad (a rhythmic prelude which sets the mood), Darāmad (rhythmic free motif), āvāz (improvised rhythmic-free singing), Taṣnīf (rhythmic accompanied by singing, an ode), Chahārmeżrāb (rhythmic music but rhythmic-free or no singing), Reng (closing rhythmic composition, a dance tune). A performance forms a sort of suite. Unconventionally, these parts may be varied or omitted. Today, rhythmic pieces are performed in beats of 2 to 7 with some exceptions. Rengs are always in a 6/8 time frame. Many melodies and modes are somehow related to the maqāmāt of the Turkish classical repertoire and Arabic music belonging to various Arab countries. This similarity is because of the exchange of musical science that took place in the early Islamic world between Persia and her neighboring countries. During the meeting of The Inter-governmental Committee for the Safeguarding of the Intangible Heritage of the United Nations, held between 28 September – 2 October 2009 in Abu Dhabi, radifs were officially registered on the UNESCO List of the Intangible Cultural Heritage of Humanity.
The music is vocal based. A large number of musical phrases when improvising a piece of Iranian music are based on Persian classical poetic prosody. In some taṣnīf songs, the musicians may accompany the singer by singing along several verses. The group of musicians and the vocalist decide on which Dastgahs and which of their Gushehs to perform, depending on the mood of a certain time or situation as they believe that special intervals in each Dastgah and Avaz can make special feelings of happiness, sorrow, epic, etc.