An electronic musical instrument, comprising: a playing operator with which pitch information indicating a certain pitch is associated; a memory that stores excitation signal waveform data, which has been previously generated from waveform data items respectively different from each other in sound intensity in the certain pitch, by adding respective waveform portions of the waveform data items so that each of the sound intensities is changed along a temporal sequence similar to the progress of a stored address, wherein the waveform data stored in the memory has been preliminarily subjected to window-multiplying processing and unnecessary frequency components have been removed therefrom; and a sound source which performs processing of: receiving, in response to a user operation on the playing operator, a sound generation instruction according to playing operation information including the pitch information indicating the certain pitch and sound volume information indicating a certain volume, changing a read-start address for reading a waveform data portion from the waveform data stored in the memory, according to the sound volume information, generating excitation data by multiplying partial data by a window function, the partial data being read sequentially from the changed address, wherein a time width of a waveform of the partial data read in the sound source differs in accordance with the pitch information, and a time width of a window of the window function also differs in accordance with the pitch information, and generating sound according to the certain pitch by a string model, based on the excitation data. a playing operator with which pitch information indicating a certain pitch is associated; a memory that stores excitation signal waveform data, which has been previously generated from waveform data items respectively different from each other in sound intensity in the certain pitch, by adding respective waveform portions of the waveform data items so that each of the sound intensities is changed along a temporal sequence similar to the progress of a stored address, wherein the waveform data stored in the memory has been preliminarily subjected to window-multiplying processing and unnecessary frequency components have been removed therefrom; and a sound source which performs processing of: receiving, in response to a user operation on the playing operator, a sound generation instruction according to playing operation information including the pitch information indicating the certain pitch and sound volume information indicating a certain volume, changing a read-start address for reading a waveform data portion from the waveform data stored in the memory, according to the sound volume information, generating excitation data by multiplying partial data by a window function, the partial data being read sequentially from the changed address, wherein a time width of a waveform of the partial data read in the sound source differs in accordance with the pitch information, and a time width of a window of the window function also differs in accordance with the pitch information, and generating sound according to the certain pitch by a string model, based on the excitation data. receiving, in response to a user operation on the playing operator, a sound generation instruction according to playing operation information including the pitch information indicating the certain pitch and sound volume information indicating a certain volume, changing a read-start address for reading a waveform data portion from the waveform data stored in the memory, according to the sound volume information, generating excitation data by multiplying partial data by a window function, the partial data being read sequentially from the changed address, wherein a time width of a waveform of the partial data read in the sound source differs in accordance with the pitch information, and a time width of a window of the window function also differs in accordance with the pitch information, and generating sound according to the certain pitch by a string model, based on the excitation data.