A musical piece correction apparatus corrects a sounding timing (note-on timings) of a sound constituting apart of a musical piece. First, the musical piece correction apparatus reads, from storage means, music performance data indicating sounding timings in the musical piece. Next, the musical piece correction apparatus sets a plurality of reference timings (grids) in a performance period of the musical piece, and sets, for each reference timing, a reference period (area) including said each reference timing. At this point, from among sounding timings included in the reference period, a nearest sounding timing to said each reference timing is selected, and the selected sounding timing is corrected so as to coincide with said each reference timing.