Having now checked the citation provided by Not as well informed as WIY, I am more convinced that I am correct. The Machzor Vitry clearly says that after benching, the bride would be brought to the men and seated opposite the groom. Then young men and boys would dance before the couple and sing their praises. That custom is better reflected in the practice in Modern Orthodox and some Yeshivish weddings where during the first dance the bride comes and sits next to the groom and men dance before them. The Machzor Vitry does not at all address the Chassidic practice of a man dancing with/before the bride while they both hold a gartel or sash. And BTW R. Gross does not use the reference to the Machzor vitry as a basis for the Mitzvah Tantz. Rather he uses the reference to strengthen his view that other women should not be present during the dance and that the mechitza should not be opened for the dance. What is the basis of the current chassidic practice? It most definitely is not the Machzor Vitry. I stand by my theory until someone provides a text proof that pre-dates the Besht, for the mitzvah tantz as practiced by Chassidim today.
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