The ornamental design for a keyboard and stand, as shown and described.
FIG. 1 is a perspective view of the keyboard and stand, in a closed state, showing my design thereof;
FIG. 2 is a perspective view thereof in a partially open state;
FIG. 3 is a perspective view thereof in a further partially open state;
FIG. 4 is a perspective view thereof in an open state;
FIG. 5 is a top view thereof in an open state without the stand;
FIG. 6 is a front view thereof in an open state without the stand;
FIG. 7 is a side view thereof in an open state without the stand; and,
FIG. 8 is a bottom view thereof in an open state without the stand.
The keyboard stand is shown in broken lines in FIGS. 1-4 for environmental purposes only and forms no part of the claimed design. The portions of the keyboard shown in broken lines form no part of he claimed design.