Meru is used to describe the quality of both the vocals and music. It is used in contrast to haru, which indicates an increase in the strength of the vocals or music, to describe when the sound becomes lower or weaker. Humidity has a large effect on the kotsuzumi and ōtsuzumi. When it increases, the skin on the drums becomes loose, and the sound becomes duller, “the leather is meru” is used, and conversely, when it dries out and the sound becomes sharper and less profound, “the leather is haru” is used.