plainsong

詳細解釋：

plain.song

n.Roman Catholic Church （名詞）【羅馬天主教】

A Gregorian chant.
格列高利聖歌
A melody to which contrapuntal voices are added in Gregorian chant.
素歌：加入對位音調的格列高利聖歌的曲子
Any medieval liturgical music without strict meter and traditionally sung without accompaniment.Also called In this sense, also called plainchant
平旋律聖歌：中世紀禮拜儀式音樂，毫無強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
中世紀拉丁語 cantus pl3nus的翻譯