PURPOSE: To create a base pattern with full of variety by using a neural network and a correcting means for correction in accordance with a parameter which is given by use of the neural network.

CONSTITUTION: In a parameter normalizing device 2, an output interpreting device 6 for normalizing a parameter delivered from a parameter designating device 1 into a value in a range of 0 to 1 converts an output pattern into music performance data. An output compensating device 9 carries out determination based upon a rhythm or a musical rule so as to correct a disadvantage part. A performance data synthesizing device 12 receives data from the device 9, and converts performance data from a code designating device 13 so as to synthesize performance data in consideration with the code, and thus obtained performance data are inputted to a performance device 14 which therefore issues music sound. Since a network 3 is connected with weighing data memory 4 and a weighing data change-over circuit 5, and the device 6 is connected with an interpreted knowledge memory 7 and an output interpreted knowledge change-over device 8 while the circuit 9 is connected with a compensated knowledge memory and an output compensated knowledge change-over device 11, it is possible to create an optimum pattern with a parameter imaged by the player and to correct a musically imperfect part.