Storage medium storing music playing program, and music playing apparatus

A music playing apparatus for making a player play a melody of a predetermined piece of music, the music playing apparatus comprising:

• music data storage memory for storing music data which indicates at least a pitch of each of sounds which form the melody of the predetermined piece of music and an output timing to output each of the sounds;
• a detector for sequentially detecting, among the sounds included in the music data, a target sound which is a sound an output timing of which comes after start of playing by the music data;
• input acceptance programmed logic circuitry for accepting an input from an input device of the music playing apparatus;
• first sound output programmed logic circuitry for outputting the target sound in the case where the input accepted by the input acceptance programmed logic circuitry is a first input when or after the output timing of the target sound detected by the detector comes,
• ad-lib sound determination programmed logic circuitry for determining a pitch of an ad-lib sound as an arbitrary sound in the case where the input accepted by the input acceptance programmed logic circuitry is a second or later input after the output timing of the target sound detected by the detector comes;
• and
• second sound output programmed logic circuitry for outputting the ad-lib sound at the pitch which is determined by the ad-lib sound determination programmed logic circuitry.