A resonance tone generation apparatus 20 is applied to an electronic musical instrument DM having a tone generator for generating, in accordance with a tone generation instruction signal having a key number n, a musical tone signal indicative of a piano sound having a key tone pitch specified by the key number. In the resonance tone generation apparatus 20, the key numbers n are assigned. The resonance tone generation apparatus 20 has a plurality of resonance tone generation circuits 30(n) each being configured to have a plurality of resonance frequencies and each retrieving a musical tone signal indicative of a musical sound of the piano and generating a musical tone signal indicative of a resonance tone which imitates a sound of strings of the piano, the sound being resonated by the piano sound indicated by the retrieved musical tone signal. The resonance tone generation apparatus 20 also has a resonance circuit setting portion 60 which allows respective resonance frequencies of the resonance tone generation circuit 30(n) to coincide with frequencies of a fundamental tone and overtones of a musical sound PS(n) generated by the tone generator in accordance with tone generation instruction information including the key number n.