Abstract: Two waveshapes corresponding to an attack portion and a part of portion succeeding the attack portion of a tone to be produced are stored in a waveshape memory. The waveshape of the attack portion is read out once and thereafter the other waveshape is repetitively read out. In order to connect smoothly the repetitively read out waveshape, an interpolation operation is performed in specified sections at the end and at the beginning of the waveshape. A tone waveshape to be finally formed is constituted by the other waveshape itself in other section than the specified sections and by a new waveshape formed by the interpolation operation in the specified sections in the other waveshape, thereby realizing the smooth connection of the repetitive read out waveshapes.