MUSIC THEORY

Mod 18

• Subject of the Day: Basic Chords
• Reading Assignment: Textbook, pp. 57-64
• Written Assignment: Workbook, Ex. 4-1
• Semester Schedule

If we construct a triad on each note of the staff, the result will be as follows:

A triad may be built upon each note of a scale.  In a major key if a triad were built upon the tonic note, we would say that the triad is a tonic chord.  A triad built upon the second scale degree is a supertonic chord.  A triad built upon the third scale degree is a mediant chord, and so on.  In written analysis we convert these scale degrees into Roman numerals, e.g. 1 = I, 2 = II, 3 = III, etc.  Furthermore, both upper case and lower case Roman numerals are used.  The number designating a major triad is always upper case, e.g. 4 = IV.  The number designating a minor triad is always lower case, e.g. 2 = ii.  The diminished triad is represented with a lower case number followed by the superscripted diminished symbol, e.g. vii^o.  The augmented triad is upper case number followed by a superscripted +, eg. III⁺.  In the case of a major key the diatonic triads will be as follows: 

As you can see, the diatonic chords in a major key are these seven: the tonic triad is always major; the supertonic is always minor; the mediant, minor; subdominant, major; dominant, major; submediant, minor; and leading tone chord, diminished.

In a minor key, because of the possibilities of using either the natural submediant or the raised submediant, and the subtonic or the leading tone, many possible triads result (13).  Each has a valid claim to being diatonic, since all of these sixth and seventh degree notes are part of a minor scale.  Nevertheless, the most common chords in a minor key are as follows:

So the diatonic triads that most commonly occur in minor keys are these seven: the tonic triad is minor; the supertonic is diminished; the mediant, major; subdominant, minor; dominant, major; submediant, major; and leading tone, diminished.

If you still have questions, contact Dr. Bartolotta at wbartolo@odu.edu