monotone (n.)

"音乐或说话中不变的音调，以单调的音高发声"，1640年代； 参见 monotony。《牛津英语词典》称该词作为名词的用法是英语特有的。

Monotone is a natural device for increasing the sonority of the voice, so that it may readily fill a large space, and is also thought by some to have a peculiar solemnity of effect. It is much used as an element in chanting. [Century Dictionary]

单调音是增加声音的自然装置，使其可以轻松地填满一个大空间，并且被一些人认为具有独特的庄严效果。它在圣歌中被广泛使用。[世纪词典]