A performance control apparatus which can reflect operations carried out by a user on variations in dynamics in real time to achieve performance expressions such as crescendo and decrescendo. A keyboard generates performance timing information in response to performance operations by a user, and performance intensity information. An HDD stores data of a music piece. The data of the music piece is read out from the HDD at a tempo based on the performance timing, and sounding instruction data including information on intensities and volumes of musical tones is generated. If the performance timing coincides with timing in which note information on a musical tone is read out, the sounding instruction data on the musical tone is determined based on the performance intensity information and the volume and intensity of the musical tone included in the read note information. If the performance timing is during sounding of a musical tone based on the note information previously read out, the sounding instruction data is redetermined based on the volume information on the musical tone based on the performance intensity information in the performance timing.