The Otamatone is an electronic musical synthesizer. The Otamatone is a singing toy whose body is shaped like an eighth note (it also somewhat resembles a tadpole, "otamajakushi" being Japanese for "tadpole"), with sound emerging from a "mouth" on the notehead. The sound made by this toy can be compared to the sound of a theremin, synthesizer, or jinghu.
Video: Hallelujah - Otamatone Cover
It was developed in Japan in 1998 by the CUBE toy company and the Maywa Denki design firm. It requires two hands to play: while one hand holds and squeezes the "head", the other hand controls the pitch of the tune by placing the finger on a ribbon controller on the stem; a higher position on the stem creates a lower sound. The ribbon controller is deliberately delinearized to resemble a guitar, so there is a shorter distance between higher notes than between lower ones. Varying the pressure on the head (thereby opening and closing the "mouth" of the Otamatone) creates a wah-wah effect, and shaking the neck (and thereby slightly changing pressure on the head) creates a vibrato effect. Switches on the back of the head allow users to change octave, turn it off or on, or change the volume.