In an electronic musical instrument, when a musical tone delay time T1 read from a delay time table TBL depending on a velocity generated by a key being pressed has elapsed, a hammer string-striking sound is generated from musical tone waveform data selected in correspondence with the velocity. At the same time, when an impact delay time T2 read from the delay time table depending on the velocity has elapsed, a shelf board impulsive sound is generated from impact waveform data. The generated hammer string-striking sound and shelf board impulsive sound are added and outputted. As a result, a relationship between the shelf board impulsive sound and the hammer string-striking sound is simulated, and tone variations of an acoustic piano are reproduced.