A music learning aid to assist musicians in learning and using music theory. The music learning aid includes a semicircular folding substrate and two circular and substantially concentric discs having progressively smaller diameters. The substrate and discs are secured together at a central point such the discs are independently rotatable. By rotation and alignment of selected discs the user is able to determine chords, scales and notes associated with musical works. The device allows the user to transpose music from one key to another, as well as transposing chords, scales or intervals.