Eeroch Mahlal Nivi Lichvod HaKadosh Ribi Yaakov Abuhatzeira - אערוך מהלל ניבי לכבוד הקדוש רבי יעקב אבוחצירא
As one of my all time favorites, this song goes down in the record books for the most sung piyut for a hilula; any hilula that is. Composed by Rabbi Yaakov Ben-Atar in honour of the Rabbi Yaakob Abuhatzeira zt"l, Moroccan Jews around the world wait for the 20th of Tevet to celebrate his life and the ceremony is culminated by singing this piyut.
There have been many adaptations to the song in recent years. Some have changed the tune, some have altered the words to fit their own respective tzadik, but I assure you this is the original.
The maqam is Iraq (as are many songs of the hilula).