The genres of Tang poetry are:
Five-character ancient style
Seven-character ancient style
Eight-sentence five-character verse
Seven-syllable/seven-syllable metrical poem
classical poem with four five-character lines
heptasyllabic/seven-syllable quatrain
Five-character rule
Seven-character law
Ancient quatrains don't need antithesis, just metrical poems. If the rhyming quatrains stop the first pair and the second pair, the antithesis is unnecessary.