I have probably read and taught on the book of Psalms more than any other book in the Bible, and I find myself returning there again and again. I think it’s the idea of setting to music and poetry everything that a person can experience in life. Nothing is left out, nothing ignored or outside the scope of prayers. Everything can be said or sung, even the unsayable – if you know what I mean.
Heschel was a poet who loved to sing, and he loved nigunim, a form of Jewish religious music which wikipedia defines thus,
Nigun (pl. nigunim) [Hebrew: ניגון] is a Hebrew term meaning “humming tune.” Usually, the term refers to religious songs and tunes that are sung by groups. It is a form of voice instrumental music, often without any lyrics or words, although sounds like “bim-bim-bam” or “Ai-ai-ai!” are often used. Sometimes, Bible verses or quotes from other classical Jewish texts are sung repetitively in the form of a nigun. Nigunim are largely improvisations, though they could be based on thematic passage and are stylized in form. Nigunim are also sung as a Jewish prayer in the form of a lament. Other nigunim may be joyous or victorious.
Prayer and singing go together in Jewish spirituality, and I think this is extraordinarily healthy. Heschel writes in Man’s Quest for God,
There are three ways in which a man expresses his deep sorrow: the man on the lowest level cries; the man on the second level is silent; the man on the highest level knows how to turn his sorrow into song. True prayer is song.