To enable a player to make the similar playing with the same gestures regardless of playing places.

An insole is bisected to a front part 2 and a rear part 3, both of which are connected to a size adjusting part 4. The front part 2 and the rear part 3 are provided with a first sensor part 10 or second sensor part 20 attachably and detachably in their arbitrary positions. A foot sensor 1 formed as such insole is mounted within shoes and is operated when the sensor parts 10, 20 are pressed by the feet. In such a case, the musical tone control signals outputted from the sensor parts 10, 20 are similar if the gestures are the same regardless of the hardness of the floor of a playing place. Then, the playing is carried out in the same manner regardless of the floor.