Chabad chassidim have always followed the teaching of the Alter Rebbe that during tefillah one should totally immerse one’s self in thoughts of the Majesty of the Creator and the insignificance of the human being. This comparison subsequently evokes yearning for a fusion with the Hashem through His Torah and Mitzvos. It is these sentiments and passions which the chassid expresses while singing an emotion-laden melody, signifying his spiritual attachment to the A-lmighty. These melodies are commonly referred to as niggunei dveikus (literally, cleaving). They are often short, sometimes just a note or two.