noun, noun or participle which takes 'suru', transitive verb
humming; singing softly
Literary or slightly formal word for humming or singing quietly to oneself. In everyday speech, 鼻歌を歌う or 小声で歌う are more common.
彼は散歩しながら低唱していた。
He was humming to himself as he walked.
彼女は子守唄を低唱
She softly sang a lullaby.