For Shabbat Zakhor, the Shabbat prior to Purim, Maqam SIGAH is applied according to all Aleppo sources. The Talmud says (TB Shabbat 88a) that during Matan Torah, Israel accepted the Torah by force (like a mountain that would fall on them if they didn't accept it). However, in the days of Mordekhai, the people returned and accepted the Torah on their own; not by force. As a reminder that they returned to the Torah, we pray in Maqam Sigah, the maqam that is the same as the reading of the Ta'amim of the Torah. Another explanation for SIGAH is because the Iraqi chant of Megillat Esther is in Maqam SIGAH, whereas the Syrian chant is in Maqam SABA-MOUHAYAR/RAST. Regardless, most pizmonim for Purim are located in the Maqam Sigah section of the pizmonim book, pages 459-467.