Harmony: Introduction to Chords and Triads

In music theory, a chord is a group of three or more pitches sounding together (harmonic), or one after another (melodic). While any combination of three or more pitches may be called a chord, our music system, called tonal harmony, emphasizes chords built on the interval of a third (see the music theory lesson on intervals for review). Another name for harmony based on thirds is tertian harmony.

Triads

A triad is a 3-note chord made up of all thirds, from the lowest note to the highest. The bottom note, called the root, is the letter name of the triad. The middle note is the third because it is a third above the root. The top note is the fifth because it is a fifth above the root.

There are four possible ways to combine major and minor thirds to create triads. These combinations, called triad quality, result in major, minor, diminished, and augmented triads. Following are several methods to learn all of the possible triads. Use the method that is easiest for you. But as with any concept in music theory, the goal is to know the triads.

Major Triads

A major triad is a major third from the root to the third, and a minor third from the third to the fifth. The root to the fifth spans a perfect 5th:

Here is how a C major triad (abbreviation: CM or C) looks and sounds on the piano:

Major triads correspond to scale degrees 1,3, and 5 of the major scale with the same letter name as the triad. (i.e., a C major triad is -- of a C major scale.)

When a major triad’s root letter is C, F, or G, all three chord members (root, third, and fifth) have the same accidental:

When a major triad’s root letter is D, E, or A, the third of the triad is one accidental higher than the other chord members. Note that some of these triads aren’t very common, or are enharmonic equivalents to other triads (e.g., E-sharp major is the same as F major), but I have included them to demonstrate the concept:

When a major triad’s root letter is B, the third and the fifth of the triad are one accidental higher than the root:

Minor Triads

A minor triad is a minor third from the root to the third, and a major third from the third to the fifth. The root to the fifth spans a perfect 5th:

Here is how a C minor triad (abbreviation: Cm or c) looks and sounds on the piano:

Minor triads correspond to scale degrees 1,3, and 5 of the minor scale with the same letter name as the triad. (i.e., a C minor triad is -- of a C minor scale.)

When a minor triad’s root letter is C, F, or G, the third of the triad is one accidental lower than the other chord members:

When a minor triad’s root letter is D, E, or A, all three chord members have the same accidental:

When a minor triad’s root letter is B, the fifth of the triad is one accidental higher than the root and the third, which have the same accidental:

Diminished Triads

A diminished triad is a minor third from the root to the third, and a minor third from the third to the fifth. The root to the fifth spans a diminished 5th:

Here is how a C diminished triad (abbreviation: c° ) looks and sounds on the piano:

The best way to spell diminished triads is to start with a minor triad, then lower the fifth by one half step.

Augmented Triads

An augmented triad is a major third from the root to the third, and a major third from the third to the fifth. The root to the fifth spans an augmented 5th: