An electronic musical instrument includes a keyboard, a sound-producing system, and a control unit. A panning value indicating a left-right balance of sound outputted from a left speaker and a right speaker in stereo sound production is assigned to each key of the keyboard such that the left-right balance of soundboard resonant sound waveform data for certain higher-pitch keys is shifted towards the left-speaker as compared with the left-right balance of soundboard resonant sound waveform data for certain lower-pitch keys that are located to the left of the higher-pitch keys so as to produce realistic piano sound mimicking an actual piano.