Bayati (maqam)
Bayātī (Arabic بياتي), also known as Bayat and Uşşâk (Ushaq), is the name of a maqam (musical mode) in Arabic, Turkish, and related systems of music. Bayati is similar to a natural minor scale, with the primary exception of a half-flat second degree. The maqam is immensely popular in the Arab world, particularly in the Levant. In secular settings, it is favored in dabke and pop music. Bayati is also used very often in religious liturgies of the Middle East. It is the favored maqam of use for the adhan in Medina, Saudi Arabia. Syrian Jews have  an abundance of pizmonim in this maqam and usually apply it to all Bar Mitzvahs and to Saturday Night services. According to the Assyrian Church of the East, this mode is called Qadmoyo (first). Related maqamat are Husseini and Bayati Shuri. Nucleus. The central tones of a maqam are created from two different intervals. The eleven central tones of the maqam used in the phase sequence example above may be reduced to three which make up the "nucleus" of the maqam: The tone rows of maqamat may be identical, such as maqam bayati and maqam 'ushshaq turki: But be distinguished  by different nuclei. Bayati is shown in the example above, while 'ushshaq turki is: (H-F) is Half-Flat (keep in mind that flat lowers the note half step down, Half flat means the note is lowered 1/4 step down). (H-S) is Half-Sharp (Sharp raises the note half step up, half sharp raises it 1/4 step up). Quartertone Intervals are not fixed. A general rule: They tend to be less flat while playing an ascending phrase and vis-à-vi. Those intervals also differ from region to region. In Turkish Ottoman music, the Beyati quartertone is generally played  slightly less flat than the ‘darker’ Ussak tone.