Musical teaching device for tonality study - has rotary mask revealing tonality relationships on three concentric disc areas

摘要

The face of the thin disc (1) has three concentric annular zones (3, 4, 5) inscribed on it. The first zone (3) carries indications of tonality, the second (4) key signatures of the tonalities and the third (5) the characteristic note of the mirror tones. The face of the disc (1) is covered by a mask (2) which rotates with respect to the disc around the centre of the zones (6). The angular disposition of the three windows (7, 8, 9) on the disc and the three elements corresponding to the same tonality on the disc are the same, so as to display at the windows for each tonality, in a different position of the disc with respect to the mask, the elements corresponding to this tonality.