Two-dimensional display section is provided near a keyboard, and, in accordance with performance data, this display section is caused to effect a dynamic display moving, in a given two-dimensional trajectory, from a first display position corresponding to a key to be currently depressed to a second display position corresponding to another key to be next depressed. Thus, a human player can readily intuitively predict the key to be next depressed and depression timing of the next key, in accordance with the display drawing a so-called bouncing-ball-like two-dimensional trajectory that appears as if a ball were bouncing. Further, with a performance guide by the non-conventional or novel bouncing-ball-like two-dimensional trajectory display, the human player can enjoy continuing to play the keyboard, without getting bored, as if the player were following a bouncing ball.