Abstract: The invention refers to a chord key for musical instruments comprising a number of plastic sheets (1) that are rotatably connected together about a common axis and provided with marks (7) to show fingering positions on the instrument for the positions of the notes included in various chords. Each sheet (1) with fingering marks for note positions is transparent and corresponds to all possible positions for a particular note in various chords, and is also provided with its own special mark for differentiating between the various possible grips of the chord. A bottom sheet (2) is likewise rotatably attached to the other sheets and depicts the fretboard or manual of the instrument, whereby all possible fingering positions for a particular chord in which particular notes are included, are obtainable by turning those sheets out that correspond to the notes of the chord and by positioning these sheets on to of the fretboard sheet.