Abstract: A system for devising a sheet of music and for transposing the music from one key to another. A layer of opaque material having standard music indicia disposed thereon is interposed typically between a first and second overlay of transparent material which includes additional musical indicia. Additional indicia disposed on the overlays transparent is in the form of opaque areas which match the color of the opaque material. Cooperating indicia in the opaque layer and transparent overlays permit alignment of the two for a desired key. The aligning indicia are disposed in predetermined relationship to the staff lines and other music notations such that when the opaque layer is adjusted relative to the transparent overlay, any one of the 13 possible keys can be selected. The dimensional relationships among the various music notations and staff lines, for one embodiment, reflect the difference in relative motion between the opaque layer and each of the transparent overlays.