PURPOSE: To start a musical performance practice with a music having difficulty corresponding to a decrease in musical performance level with the elapsed time from a last practice chance to a current practice chance.

CONSTITUTION: When a start switch is turned on at the start of the musical performance practice, the result of a decision in SA1 becomes YES and a start flag is set (SA6); and the clocked value (time value from the end of the last performance practice to the start of the current practice) of a timer counter is transferred to a register Ta (SA7). Then, when the time interval from the last practice to the current practice is large and the decision result of SA8 is YES, the value of a level counter L is decreased (SA9), so that music data on the music having the same level value with the value of the level counter L are transferred from a ROM to a working RAM (SA11). The music data transferred to the working RAM are used to perform a mistake counter measuring process (SA12), thereby counting a musical misperformance.