I. plain ‧ chant /ˈpleɪntʃɑːnt $ -tʃænt/ BrE AmE noun [uncountable]
↑ plainsong
II. plain ‧ song /ˈpleɪnsɒŋ $ -sɒːŋ/ BrE AmE ( also plainchant ) noun [uncountable]
a type of old Christian church music in which people sing a simple tune without musical instruments