In traditional music theory within the English-speaking and Dutch-speaking world, pitch classes are typically represented by the first seven letters of the Latin alphabet (A, B, C, D, E, F and G). A few European countries, including Germany, adopt an almost identical notation, in which H is substituted for B (see below for details). However, most other countries in the world use the naming convention Do-Re-Mi-Fa-Sol-La-Si, including for instance Italy, Spain, France, Romania, most Latin American countries, Greece, Bulgaria, Turkey, Russia, and all the Arabic-speaking or Persian-speaking countries .
In Italian, Portuguese, Spanish, French, Romanian, Greek, Russian, Mongolian, Flemish, Persian, Arabic, Hebrew, Bulgarian and Turkish notation the notes of scales are given in terms of Do-Re-Mi-Fa-Sol-La-Si rather than C-D-E-F-G-A-B. These names follow the original names reputedly given by Guido d'Arezzo, who had taken them from the first syllables of the first six musical phrases of a Gregorian Chant melody Ut queant laxis, which began on the appropriate scale degrees. These became the basis of the solfege system. "Do" later replaced the original "Ut" for ease of singing (most likely from the beginning of Dominus, Lord), though "Ut" is still used in some places. "Si" or "Ti" was added as the seventh degree (from Sancte Johannes, St. John, to whom the hymn is dedicated). The use of 'Si' versus 'Ti' varies regionally.
The two notation systems most commonly used nowadays are the Helmholtz pitch notation system and the Scientific pitch notation system. As shown in the table above, they both include several octaves, each starting from C rather than A. The reason is that the most commonly used scale in Western music is the major scale, and the sequence C-D-E-F-G-A-B (the C-major scale) is the simplest example of a major scale. Indeed, it is the only major scale which can be obtained using natural notes (the white keys on the piano keyboard), and typically the first musical scale taught in music schools.
In a newly developed system, primarily in use in the United States, notes of scales become independent to the music notation. In this system the natural symbols C-D-E-F-G-A-B refer to the absolute notes, while the names Do-Re-Mi-Fa-So-La-Ti are relativized and show only the relationship between pitches, where Do is the name of the base pitch of the scale, Re is the name of the second pitch, etc. The idea of so-called movable-do, originally suggested by John Curwen in the 19th century, was fully developed and involved into a whole educational system by Zoltán Kodály in the middle of the 20th century, which system is known as the Kodály Method or Kodály Concept.