Musical Keyboard Pattern Cards designed to train musical keyboard students to learn the majorminor tonal system of scales and chords upon which Western music is based. The shield restricts access to the connector from environmental effects, and more specifically, restricts access to the connector from an unauthorized user. A plurality of first passageways is defined in the first housing and communicates with the slots. An engagement subsystem configured to engage sides of the film and a sealing subsystem configured to seal the film are mounted to the cross members. The reflective mirror structure includes a frame and a mirror body, wherein the frame is pivotally connected to the first surface, the mirror body is mounted on the frame, and the mirror body selectively corresponds to one of the front side and the back side. This operation allows resistor layers beneath the resistor sheet to directly contact annular electrically conductive layers facing the resistor layers in a desired sequence, respectively.