Niggunim

A niggun is a Jewish religious wordless tune that is chanted over and over. There is power to the melody, hidden meanings conveyed nonverbally.

The word 'niggun' means tune or melody; niggunim is the plural in Hebrew.

They hold a special place for gatherings of Jews the world over, and have a special place among the Chassidic communities especially. The belief is that when you sing a niggun, the soul of the rabbi who created it appears in the room. On festive occasions the niggunim have particularly joyful melodies.

Some other niggunim are used in individual prayer or devekut. Plenty more to read, listen to on this subject!