Chord and scale calculator

Step diagram Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser (Click here to install Java now)
1) Set the key

2) Select a root note

3) Select a chord or scale




4) Select a fitting chord or scale




Sort list by root note.
Global controls Use alternate polygon type. Mark each step using arrows.

Description:

This is a musical chord and scale calculator. It allows you to select an interval, chord or scale and find the chord(s) or scale(s) possessing coincident notes or intervals. For instance, the Major seventh chord (maj7 or M7) is based on the Major triad, with an additional Major seventh interval added on to it. Therefore, it will be displayed when finding the matching or fitting objects for the Major triad. Further, the interval between the second and third steps of this chord is a minor third; therefore, the minor third interval will be displayed as well.

Directions:

  1. Set the key in form #1. This rotates the entire diagram so that the selected note is at the top of the circle. (Note that the term "key", as it is used in this document, is not related to the key signature.)
  2. Set a root note in form #2. Each chord or scale has a root note. Set this in the second form field. You can set the root note to match the setting for key by clicking on the "Match key" button.
  3. Select a chord or scale in form #3.
  4. Find fitting chords or scales. This command will display a list of chords or scales in form #4 that are calculated to be contained within or outside of the selected chord or scale. You can confirm this by checking whether the polygon for a chord is contained within the polygon of the fitting scale, for instance.
  5. Hide or show objects. You can make an interval, chord or scale visible/invisible in the diagram by clicking on the "Display/reset selected object" and "Clear selected object" buttons.
  6. You can also move each object around the circle using the mouse by dragging the point in the diagram that is labeled the same as the object.

Issues:

  1. Dragging the objects around the circle does not update the form fields. (I'm considering whether it should, in fact, do so.)
  2. A convex polygon may not be the best representation for a chord or scale when the interval between steps is greater than six semitones.
  3. Related to the above is the issue of how best to represent steps that lie in another octave. I've considered labeling each step or changing the lightness and darkness of the color depending on the octave. However, I'm not sure this is achievable in GeoGebra.
  4. Minor and major objects are typically capitalized with a lower-case or capital "m" depending on whether the component chords or intervals are minor or major, respectively. I've chosen to disregard this naming scheme.

You can download an old Geometer's Sketchpad version of this worksheet, here.

Created by Michael Horvath using GeoGebra. Last modified: Monday, 08-Dec-08 13:27:15 PST

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