Koron and Sori: The Microtonal Accidentals of Persian Music

Persian classical music uses pitches that do not exist on a piano. The neutral seconds, flexible thirds, and mutable intervals that define each dastgah fall between the notes of Western twelve-tone equal temperament. To notate these pitches on the Western staff, Persian musicians use two special accidental symbols: the koron and the sori. They are simple, practical, and in continuous use for over a century — but the pitches they represent are more complex than the symbols suggest.

What koron and sori do

Established The koron lowers a note by approximately a quarter tone. The sori raises a note by approximately a quarter tone. Together with the standard Western natural, sharp, and flat, they give Persian notation five levels of pitch alteration for any note name. This is enough to represent all the pitches used in the dastgah system.

Established In visual appearance, the koron is written as a short vertical line with a small open triangular head pointing to the upper right. The sori resembles a "greater than" sign (>) crossed by two short vertical lines. Both symbols are positioned on the staff like standard accidentals — to the left of the note they modify.

Established Both symbols were added to the Unicode Standard in version 14.0: sori as U+1D1E9 (MUSICAL SYMBOL SORI) and koron as U+1D1EA (MUSICAL SYMBOL KORON). Their inclusion in Unicode enables their use in digital music software and scholarly typography without requiring custom font workarounds.

Vaziri's invention

Established The koron and sori were introduced by Ali-Naqi Vaziri (1886-1979), the most influential figure in the modernization of Persian music theory. Vaziri published Dastur-e Tar, his instruction book for the tar, in Tehran in 1913 — the first systematic transcription of Iranian classical music into Western staff notation. To handle the microtonal pitches that standard notation could not express, he devised the two new accidentals.

Established Vaziri's broader theoretical project went beyond notation. He proposed dividing the Persian octave into twenty-four equal quarter-tone steps, a system that would allow Western harmonic techniques to be applied to Persian melodies. In this framework, koron and sori represented exact quarter tones of 50 cents each — a clean, symmetrical extension of the Western twelve-tone system.

Attested This equal-temperament proposal proved deeply controversial. From the 1960s onward, scholars led by Hormoz Farhat argued that Persian intervals are not equal quarter tones and that forcing them into a 24-tone grid distorts the music's essential character. Vaziri's temperament theory was largely rejected by the academic and conservatory establishment. His notation symbols, however, survived the critique intact. Koron and sori remain the standard accidentals in Persian music notation today, understood as representing approximate rather than exact quarter-tone inflections.

Not exactly quarter tones

Established The word "approximately" in the definition of koron and sori is not a hedge — it is the point. Farhat's measurements of practiced intervals in Persian music, documented in The Dastgah Concept in Persian Music, show that the pitches represented by koron and sori do not correspond to a single fixed interval. The actual size of a koron inflection varies depending on the dastgah, the specific scale degree, the melodic direction, and the individual performer.

Established Farhat deliberately provides interval measurements in approximate cents rather than committing to any fixed temperament grid. A koron second in Shur, for example, is a neutral interval — larger than a Western minor second (100 cents) but smaller than a whole tone (200 cents). Its exact value is not fixed at 150 cents (the theoretical equal quarter-tone value) but falls in a range that shifts with context. This is not imprecision in the theory; it is accuracy about how the music actually works.

Attested During similarly emphasizes that Persian intonation is guided by the ear and by tradition rather than by theoretical grids. The koron symbol tells the performer that a pitch is lowered by something less than a semitone — the musical context and the performer's training determine exactly how much.

How koron and sori work alongside standard accidentals

Established In a notated Persian score, koron and sori function alongside the standard Western accidentals. This gives the system five pitch levels for any given note name:

Practice A key signature in Persian notation may include koron symbols. In Shur on D, for instance, E koron and A koron appear in the key signature, indicating that these notes are lowered throughout the piece unless otherwise marked. The visual effect is similar to reading a Western key signature — the koron symbols sit at the beginning of each staff line just as sharps and flats do in Western notation.

Moteghayyer: where notation meets its limits

Established The deepest tension in Persian notation is not between koron and sori and exact quarter tones. It is between any fixed symbol and the reality of moteghayyer — the mutable pitches that shift their intonation depending on melodic context.

Established In Shur, the second degree (E koron) and the sixth degree (A koron) are both moteghayyer. Farhat documents that these pitches shift depending on whether the melody is ascending or descending: raised slightly in ascent, lowered in descent. The notation writes both as "koron" — the same symbol — but the performed pitches are not identical. The koron symbol marks a zone of intonation, not a single point.

Practice This is why Persian music pedagogy does not rely on notation alone. The radif — the canonical repertoire that defines each dastgah — is transmitted orally from master to student. Written notation with koron and sori symbols serves as a reference and a memory aid, but the subtleties of mutable intonation are learned by ear. The symbols get you close; the tradition gets you the rest of the way.

Comparison with Turkish accidentals

Established The contrast with the Turkish Arel-Ezgi-Uzdilek system is instructive. Where Persian notation adds two microtonal accidentals to the Western set, the Turkish AEU system adds six — ten accidentals in total, keyed to the Holdrian comma (1/53 of an octave). The Turkish system distinguishes between 1-comma, 4-comma, 5-comma, 8-comma, and 9-comma alterations, providing much finer theoretical resolution.

Attested This difference reflects a philosophical divergence, not merely a notational one. Turkish theory commits to the premise that intervals are specific and countable — that the difference between a 4-comma flat and a 5-comma flat is real and notatable. Persian theory, particularly in the post-Vaziri tradition shaped by Farhat's analysis, takes the opposite view: two symbols are enough because exact interval sizes are not fixed. The precision lives in the performer's ear, not in the notation.

Practice Neither approach is superior. The Turkish system offers more theoretical resolution but implies a precision that practiced intonation does not always match. The Persian system is simpler and arguably more honest about the limits of notation, but it cannot distinguish between intervals that a Turkish score would notate differently. For students working across both traditions, understanding this difference is essential to reading scores from either one correctly.

Practical reading tips

Practice When encountering koron and sori in Persian notation for the first time, keep these points in mind:

• Koron means lower, sori means higher. Koron is a partial flat; sori is a partial sharp. Neither is a half-step — both are roughly half of a half-step.
• Check the key signature. Koron symbols in the key signature affect every occurrence of that note, just as sharps and flats do in Western notation.
• Listen, do not calculate. The symbols indicate approximate pitch zones, not exact frequencies. The correct intonation for a given koron or sori pitch depends on the dastgah and the melodic context. Use recordings of the radif as your reference, not a tuner set to 50-cent intervals.
• Expect mutable pitches. If you see E koron in a Shur piece, that pitch is moteghayyer — it will shift depending on melodic direction. The same symbol does not always mean the same pitch.