Every other liturgical chant tradition of the Christian East is monophonic at its root. Byzantine chant sets a melody over a drone, Znamenny chant is sung in unison, Coptic and Syriac chant likewise. Georgian chant is not. It is sung in three parts at once, and the parts are independent lines rather than a melody with accompaniment underneath it. The voice that carries the chant is the mtkmeli, the one that moves above it is the modzakhili, and the lowest is the bani. All three are needed for the chant to exist at all, which is why a solo performance of Georgian chant is a fragment rather than a reduction.
Two schools are distinguished, and the distinction is real enough that chanters trained in one do not simply read the other. The eastern practice, associated with Kartli and Kakheti and with the monastery of Gelati, is the plainer of the two, with the upper voices moving close to the chant. The western practice of Guria and Imereti, associated with Shemokmedi, is far more elaborate, with wider intervals, sharper dissonances and a habit of resolving onto open fifths that strikes ears trained on Western harmony as archaic rather than merely unfamiliar.
What holds them together is that both are liturgical before they are musical. The three voice texture is not a national style applied to the office. It is how the office has been sung in Georgian for as long as anyone can document, and the folk polyphony of the same regions, which UNESCO recognised in 2001, is its neighbour rather than its parent.