The kotsuzumi , or 'small tsuzumi', is one of two hand drums in the instrumental ensemble of nō. The ko-tsuzumi has an hourglass-shaped body carved from wood which is generally painted with lacquer. Drum skins made from horse hide affixed to circular frames can be fitted to the two ends of the body by lashing them together with hemp ropes. Skins and body are stored separated and assembled before each performance. The drum is held with the left hand close to the right shoulder and struck from below with the open right hand while simultaneously squeezing the lashing cords. Different sounds are produced depending on how tightly the drummer holds the cords and on the timing of squeezing the cords coordinated with the striking of the drum. To produce the varied pitches and timbres, the skins of the ko-tsuzumi need to be kept moist. One often sees the ko-tsuzumi player blow moist air on the skins or wet them with his finger during performance to ensure they remain pliable.
In nō music, the ō-tsuzumi and ko-tsuzumi function as a pair, playing together to construct the rhythmic patterns. Broadly speaking, the ō-tsuzumi takes charge of the odd number beats that form the rhythmic framework and the first half of the phrase, while the ko-tsuzumi governs the even number beats and the last half of the phrase. While the ōtsuzumi produces a sharp sound with little variation and creates the foundation of the rhythm, the ko-tsuzumi plays ornamentation between the ō-tsuzumi beats..