A display device includes a first planar surface and a second planar surface divided into a plurality of adjacent sectors, the second planar surface attached concentrically and rotatable with respect to the first planar surface, the second planar surface including at least one display window to reveal at least one portion of the first planar surface bearing harmonica note location indicia and/or harmonica position indicia corresponding to use of a harmonica, the at least one display window to reveal the harmonica note location indicia and/or the harmonica position indicia upon a substantial alignment of a sector of the first planar surface with a sector of the second planar surface.