名詞 plainsong:

1. a liturgical chant of the Roman Catholic Church
   同義詞：plainchant, Gregorian chant

plain.song

n.Roman Catholic Church （名詞）【羅馬天主教】

A Gregorian chant.
格列高利圣歌
A melody to which contrapuntal voices are added in Gregorian chant.
素歌：加入對位音調(diào)的格列高利圣歌的曲子
Any medieval liturgical music without strict meter and traditionally sung without accompaniment.Also called In this sense, also called plainchant
平旋律圣歌：中世紀(jì)禮拜儀式音樂，毫無強(qiáng)音裝飾且通常沒有伴奏也作 在此意義上也可稱作 plainchant

來源：
Translation of Medieval Latin cantus pl3nus
中世紀(jì)拉丁語 cantus pl3nus的翻譯