Introduction to Triads

In music, a chord is two or more intervals sounding together. The notes in a chord may sound all at once or appear in succession, creating an arpeggio.​

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A specific type of chord is the triad, a three-note chord that combines two 3rds, one above the other. Every triad must contain a root, third, and fifth.

In every triad, there is an interval of a 3rd between the root and the third. There is another 3rd between the third and the fifth. Finally, there is a 5th between the root and the fifth.​

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If they are in root position, meaning the root is on the bottom, they will usually be three successive lines or three successive spaces (see picture on the right).

Look at the picture on the right to see how a root position triad is made up of a third stacked on top of a third, leaving an interval of a fifth between the root and the fifth.​

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Be careful not to get confused between the intervals used to make the triad (i.e. 3rd and 5th) and the names of the triad (i.e. root, third, and fifth).

Triads are named by the letter of their root and the quality of the chord. There are four qualities for triads.​

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Major triads contain the following intervals:

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• M3 between root and third

• m3 between third and fifth

• P5 between root and fifth

Let's check one together. First, we see what the quality of the 3rd is between the root (A) and the third (C#). In the key of A major, we have 3 #'s, including C#. That means A to C# is a M3. So far so good!

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Next, we check the quality of the 3rd between the third (C#) and the fifth (E). In the key of C# major, we have 7 #'s, including E#. That means C# to E is a m3. Again, this points to a major triad.

To check our work, we measure the root (A) to the fifth (E). In the key of A major, we have 3 #'s, and none of them are E#. Therefore, A to E is a P5.​

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If our triad has a M3 with a m3 on top, and we have double checked that the root and fifth form a P5, it is a major triad.

Minor triads contain the following intervals:​

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• m3 between root and third

• M3 between third and fifth

• P5 between root and fifth

Let's check one together. First, we see what the quality of the 3rd is between the root (C) and the third (Eb). In the key of C major, we have 0 b's. That means C to Eb is a m3. So far so good!​

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Next, we check the quality of the 3rd between the third (Eb) and the fifth (G). In the key of Eb major, we have 3 b's, none of which are Gb. That means Eb to G is a M3. Again, this points to a minor triad.

To check our work, we measure the root (C) to the fifth (G). In the key of C major, we have 0 #'s and 0 b's, which means G fits the key signature. Therefore, C to G is a P5.​

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If our triad has a m3 with a M3 on top, and we have double checked that the root and fifth form a P5, it is a minor triad.

Diminished triads contain the following intervals:​

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• m3 between root and third

• m3 between third and fifth

• d5 between root and fifth

Let's check one together. First, we see what the quality of the 3rd is between the root (A) and the third (C). In the key of A major, we have 3 #'s, including C#. That means A to C is a m3. So far so good!​

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Next, we check the quality of the 3rd between the third (C) and the fifth (Eb). In the key of C major, we have 0 b's. That means C to Eb is a m3. Again, this points to a diminished triad.

To check our work, we measure the root (A) to the fifth (Eb). In the key of A major, we have 3 #'s, none of which are E#. Therefore, A to Eb is a d5.

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If our triad has a m3 with another m3 on top, and we have double checked that the root and fifth form a d5, it is a diminished triad.

Augmented triads contain the following intervals:

• M3 between root and third

• M3 between third and fifth

• A5 between root and fifth

Let's check one together. First, we see what the quality of the 3rd is between the root (E) and the third (G#). In the key of E major, we have 4 #'s, including G#. That means E to G# is a M3. So far so good!​

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Next, we check the quality of the 3rd between the third (G#) and the fifth (B#). There is no such thing as the key of G#. However, if we pretend each note is a half step lower, G# to B# becomes G to B. The distance between them is the same. The key of G has 1 # (F#). That means G to B is a M3, and G# to B# is a M3. Again, this points to an augmented triad.

To check our work, we measure the root (E) to the fifth (B#). In the key of E major, we have 4 #'s, none of which are B#. Therefore, E to B# is an A5.​

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If our triad has a M3 with another M3 on top, and we have double checked that the root and fifth form an A5, it is an augmented triad.

Since triads are named after their root and their quality, we can use lead sheet symbols (also known as pop chord symbols) to shorten their names. There are several variations for each quality, but a few of the most common are listed below. Let's use the root C as our example.​

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C major or C

C minor or Cm or C- or c

C dim or C^o

C aug or C+

Example 7.3 (comparison of the four triad qualities built on F)