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尚 supplies the sound — shàng shifting to táng in
堂 (a known sh/t alternation in this phonetic series).
尚 also adds a faint semantic flavor of 'lofty, elevated' which suits a hall: a raised, formal space. Phonetic family:
党 (party),
棠 (crab apple),
趟 (a trip),
躺 (lie down),
倘 (if).