The ornamental design for an electronickeyboardinstrument, as shown and described.
FIG. 1 is a perspective view of an electronic keyboard instrument showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is an enlarged view of an indicated portion of FIG. 5.
The dot-dashed broken line showing in the views represent boundaries of the claim and form no part of the claimed design. The two dots-dashed broken lines showing in the views represent the boundary of the enlarged portion and form no part of the claimed design. The evenly segmented dashed broken lines showing in the views are for the purpose of illustrating unclaimed subject matter only and form no part of the claimed design.