A CPU sets a first key-press pitch as a first target value; sets the immediately-preceding key-press pitch as a first starting point; emits the first key-press pitch sound therefrom with portamento toward the first target value; sets the second key-press pitch as a second target value; sets a pitch obtained by adding a pitch difference between the first and second key-press pitches to the pitch of the above-described sound as a second starting point; emits the second key-press pitch sound therefrom with portamento toward the second target value; sets the third key-press pitch as a third target value; sets a pitch obtained by adding a pitch difference between the second and third key-press pitches to the pitch of the sound being emitted with portamento toward the second target value as a third starting point; and emits the third key-press pitch sound therefrom with portamento toward the third target value.