Be sure to get a copy of our prayer book: Siddur Nishmat Kol Chai, CLICK HERE to order a copy. The Hallel are a series of Psalms that are either chanted or sung when put to music on Jewish holidays and happy occasions. They are comprised of Psalms 113-118, and when chanted all together, it is called Hallel Shalem (Full Hallel). On Pesach (Passover) and Rosh Chodesh (New Moon) the first eleven verses of Psalms 115 and 116 are omitted. This version is called Hotzi Hallel (Half Hallel). Hallel is not said on Rosh Hashanah or on Yom Kippur, due to the solemness of these days of awe, as well as it is not said on Purim, due to the fact God's Name is not mentioned in the Megillah, even though God did deliver and rescue His people, nonetheless, this is the custom.