Though the origins of Iran's modal music remain vague, research has revealed more than was previously known. Barbod the Great of the 7th Century (A.D.), a court musician of the Sassanid Empire, created the first ever musical system in the Middle East,^{[citation needed]} known as the "Royal Khosravani," dedicated to the king Khosrau II. Many current names of the modes used in Iranian classical music, dastgahs, have survived from that time by an oral tradition, though many of the modes and melodies have disappeared, probably because of Arab invaders who viewed music as immoral behavior.

Iranian classical music relies on improvisation and composition and is based on a series of modal scales and tunes which must be memorized. Apprentices and masters (ostad) have a traditional relationship which has declined during the 20th century as music education moved to universities and conservatories. A repertoire of more than two hundred short melodic movements called gusheh, which are classified into twelve dastgahs. Each gusheh and dastgah has an individual name. A typical performance consists of a pishdaramad (pre-introduction or more appropriately prelude), daramad (introduction), avaz (improvised rhythmic-free singing), tasnif (rhythmic accompanied by singing), Chaharmezrab (rhythmic music but rhythmic-free or no singing), reng (closing rhythmic). A performance forms a sort of suite. The gusheh and daramad are non-metric and rhythm-free, while the tasnif, pishdaramad, reng and chaharmezrab are rhythmic. Unconventionally, these parts may be varied or omitted. Towards the end of the Safavid Empire (1502-1736), more complex movements in 10, 14, and 16 beats stopped being performed. In fact, in the early stages of the Qajar Dynasty, the usul (rhythmic cycles) were replaced by a meter based on the ghazal and the maqam system of classification was altered to the radif system which is used to this day. Today, rhythmic pieces are performed in beats of 2 to 7 with some exceptions. Many melodies and modes are related to the maqams of Turkish and Arabic music.

Upon their invasion of the Persian Empire, the Arabs declared^{[citation needed]} the lands they conquered as their "Islamic World." Though most Arab rulers prohibited musical activity, others ordered Persian musicians to write compositions for the courts of the caliphate. Books written by Iranian musicologists, such as Farabi's Kitab al-Musiqi al-Kabir, have influenced the music cultures throughout the Islamic world.^{[citation needed]} Iranian music has influenced the music of various countries greatly since the Sassanian times,^{[citation needed]} which provides a reason why melodies within the classical music of Turkey, Syria, Iraq and Egypt bear the names of some Iranian modes.^{[citation needed]}

The classical music is vocal based. The vocalist plays a crucial role: she or he decides what mood to express and which dastgah relates to that mood. In many cases, the vocalist is also responsible for choosing the poems to be sung. If the performance requires a singer, the singer is accompanied by at least one wind or string instrument, and at least one type of percussion. There could be an ensemble of instruments, though the primary vocalist must maintain hers or his role. In some tasnif songs, the musicians may accompany the singer by singing along several verses. Traditionally, music is performed while seated on finely decorated cushions and rugs. Candles are sometimes lit. 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.

Wall painting depicting a scene from 17th century Persia.

A Sassanid era mosaic excavated at Bishapur

Before the Arab invasion, the melodies in which recitals from the Avesta were chanted or sung were fitted into modes. The term "gah" has two meanings: in the Pahlavi language, it means both "gath" (a prayer from the Avesta) and also "time." Modern day musicians tend to attribute the meaning of "gah" strictly to "time" or "place" in regards to movements on an instrument. The modes "yekgah, dogah, segah chahargah, panjgah, sheshgah, and haftgah" were used to recite gaths one through seven. Recently, it was discovered that the mode "rast" (lit. truth) was used while singing stories of truthful acts or people and "shekasteh" (lit. broken) was used in telling stories of evil doers. The mode "homayoun" was used while reciting morning prayers. Most of these modes, except probably for "sheshgah" and "haftgah" still exist in the system today. However, it is virtually impossible to know how the music sounded during that era. So while the names of the modes can be traced to antiquity, no conclusion can be reached on the similarities of their sounds. After the Sassanid era, it is obvious that newer melodies were created in various different periods, probably through hundreds of years. When Islam became the dominant religion of Iran, rulers decided to either ban music or to later discourage people from the recital of Mazdean prayers in those modes. Classical music was performed strictly in court up until the 20th century. It was performed in secret during the rule of Islamic extremists of medieval era.

Iranian classical music continues to function as a spiritual tool as it has throughout its history, and much less of a recreational activity. Compositions can vary immensely from start to finish, usually alternating between low, contemplative pieces and athletic displays of musicianship called tahrir. The incorporation of religious texts as lyrics were replaced by lyrics largely written by medieval Sufi poets, especially Hafez and Jalal-e Din Rumi.

The best reference in detailed bibliographical facts on history and effect of Persian music on other forms of classical music, like that of (Arabic-Turkish and Indian), please read Nur-Ratnakara (Ocean of Light)by the late prof. Shahab Sarmadi of AMU Aligarh India.

Major instruments

Instruments used in Persian classical music include the bowed spike-fiddle kamancheh, the goblet drum tombak, the end-blown flute ney, the frame drum daf, the long-necked lutes tar, setar, tanbur, dotar, and the dulcimer santur. The ordinary violin is also used, with distinctively Persian tuning. Harps, "chang[s]," were a very important part of music up until the middle of the Safavid Empire. They were probably replaced because of tuning problems or replaced by the qanun (zither)and later the piano which was introduced by the West during the Safavid Dynasty of Iran. Many, if not most, of these instruments originated in Iran. Perhaps the most loved string instrument is the tar. Tar players are regurlarly chosen to function as the primary string instrument in a performance. The setar is also loved for its delicacy and is the favorite among Mystic musicians. Some instruments like the sorna, neyanban, dohol, naghareh, and others, are not used in the classical repertoire but are used in Iranian Folk music. The ghazhak (ghaychak), a type of fiddle, is being re-introduced to the Classical field after many years of exclusion. The instruments used in the Classical field are also used in Iranian Folk Music.

The reference is Ghonyat-al-Monyah an aged old manuscript translated and published by the Late Prof. Shahab Sarmadi of AMU Aligarh India. This book describes in detail the history of Persian musical instruments.

Here is an example of where the links are: Prof. Shahâb Sarmadî of Aligarh Muslim University, due to his specific expertise in Persian and Indian Classical Music, translated a section called “Roots and Branches of Music,” which is a part of Volume II. When he was in Chicago for the 1987 conference he graciously agreed to stay over for a month and translated this chapter on music. This translation exposes AmÊr Khusrau’s expertise in music although he seems to attempt to avoid any credit to himself. The special feature of this translation is Amîr Khusrau’s description of a Pardah System, without mentioning the invention of sitar as an instrument. In the sitar design there are 12-13 mizrÉb, a typical form of plectrum made of steel wire played with a zamzama held in one hand that strikes against mizrÉb in a pattern creating a system of music. This system of music makes unlimited Pardah System by placing the 12-13 plectrums in various positions, thus exposing numerous potentialities. Amîr Khusrau’s ingenious definition of the Pardah System described in this section of Volume II, and equally ingenious effort by Prof. Shahâb Sarmadî in catching these in his translation enumerates value of this work. This Pardah System of music may have been easily transformed into the design of mizrâb and zamzama in sitar, when played together creating a Pardah System of music, thus providing a proof of Amîr Khusrau’s invention of sitar. It is reasonable to imagine that, because of his Turkish/Lachin (in the following introduction to I’jâz-i-Khusravî he calls himself Khusrau-Lachin) heritage, Amîr Khusrau may have been exposed to the Maqam System of Muslim Music, merging with the Sanstân System or Thât System of Music in north India and the Mela-Karta System in south India, provided a new scope of invention for Amîr Khusrau. The section on music in Vol. II is highly technical, which necessitated writing detailed footnotes by Prof. Shahâb Sarmadî resulting from our discussions.