A musical sound generation device comprising: a first memory section having a plurality of waveform data stored therein; a second memory section which stores waveform data read out from the first memory section in a manner that the waveform data is readable for sound emission by a sound emission control section; and a control section which controls such that, when an instruction for sound emission is provided and waveform data specified in association with the sound emission is in the second memory section, the specified waveform data stored in the second memory section is read out by the sound emission control section, or controls such that, when an instruction for sound emission is provided and waveform data specified in association with the sound emission is not in the second memory section, the specified waveform data is transferred from the first memory section to the second memory section and the transferred waveform data in the second memory section is read out by the sound emission control section, wherein the control section controls such that, among a plurality of waveform data stored in the second memory section, waveform data satisfying a set condition is not subjected to a change by the transfer, and waveform data not satisfying the set condition is subjected to the change by the transfer, characterized in that the control section stores, among the plurality of waveform data, waveform data having a data size exceeding a predetermined threshold value fixedly in the second memory section in a manner that the waveform data is not changed during a musical performance including the sound emission. a first memory section having a plurality of waveform data stored therein; a second memory section which stores waveform data read out from the first memory section in a manner that the waveform data is readable for sound emission by a sound emission control section; and a control section which controls such that, when an instruction for sound emission is provided and waveform data specified in association with the sound emission is in the second memory section, the specified waveform data stored in the second memory section is read out by the sound emission control section, or controls such that, when an instruction for sound emission is provided and waveform data specified in association with the sound emission is not in the second memory section, the specified waveform data is transferred from the first memory section to the second memory section and the transferred waveform data in the second memory section is read out by the sound emission control section, wherein the control section controls such that, among a plurality of waveform data stored in the second memory section, waveform data satisfying a set condition is not subjected to a change by the transfer, and waveform data not satisfying the set condition is subjected to the change by the transfer, characterized in that the control section stores, among the plurality of waveform data, waveform data having a data size exceeding a predetermined threshold value fixedly in the second memory section in a manner that the waveform data is not changed during a musical performance including the sound emission.