To provide the method and device for musical sound waveform generation which can find an optimum cross-face point with a less calculation quantity than before.

A chromosome initializer 1 generates a specified number of chromosomes within a specified range from musical sound waveform data. A correlation coefficient calculator 2 calculates a correlation coefficient regarding each chromosome. A comparison decision part 5 judges whether or not there is a correlation coefficient larger than a reference correlation coefficient 0 and when not, plural loop points are evolved through the operation of a chromosome selector 6, a crosser 7, and a mutation unit 8 through genetic algorithm so that the cross-correlation coefficient between a basic musical sound waveform and waveforms obtained on the basis of the loop points is increased, and then fed back to the correlation coefficient calculator 2. When the comparison decision part 5 decides that there is a coefficient larger than the reference correlation coefficient 0, a corresponding loop position is determined as a cross-fade point.