PURPOSE: To perform transposition of musical pieces having been program-inputted through simple key operation by obtaining the coded information after the transposition based on the coded information indicating the height of sounds and the coded information for transposition.

CONSTITUTION: Through operation of a key switch, the assigned address of an input control circuit VM is upped by the signal S1 from a sequence control circuit SN and likewise the note codes of said address are converted to the codes after transposition in the case of height codes and are directly in the case of length codes inputted to buffer registers B1, B2 respectively by the signal S2. Next, the sound source signal corresponding to the height code is outputted from a sound source signal VS by the signal S3 and at the same time the sound source signal is applied to a speaker driver D by turning ON the time gate G3 corresponding to the length code, thereby producing the desired sound from a speaker SP. When production of the sound corresponding to one note is finished, the signal from a counter content detecting circuit operates the sequence control circuit to convert desired notes to sounds until the end code is outputted, hence musical pieces are readily transposed.