This study examines the usage of ghammz (dominant note) particularly in the opening section in Arab maqm music, which has eluded the mainstream of debate in maqm theory. The concept was first introduced by Rodolphe d'Erlanger in the Congress of Arab Music held in Cairo in 1932, but never gained broad support amid the general trend towards simplification in maqm classification particularly in Cairo, where the use of ghammz is chiefly recognised as a modulation technique. This is partly because d'Erlanger's analysis was informed by the musical practice of Aleppo, which still retains subtleties in differentiating maqmt (plural of maqm, melodic mode), using the ghammz as an essential feature not only in marking transitions between maqmt in modulation but in differentiating seemingly similar modes by creating a modal feeling characteristic to each maqm in the opening section. Although these features have been transmitted empirically rather than theoretically, they stand as evidence for the continuity of an Aleppine tradition distinctive from the better-known practice centred on Cairo.