A triad is a three-note chord whose notes can be arranged in thirds. A triad can always be "stacked" so that its notes are either on all lines or all spaces.

When a triad is stacked in its most compact form in thirds, the lowest note is called the root, the middle note is called the third, and the highest note is called the fifth.

There are four qualities of triad. A major triad's third is major and its fifth is perfect, while a minor triad's third is minor and its fifth is perfect. A diminished triad's third is minor and its fifth is diminished, while an augmented triad's third is major and its fifth is augmented.

In chord symbols, major triads are represented with capital letters that correspond to the triad's root. Minor triads have a lowercase "mi" after the letter, diminished triads have a superscript circle (o), and augmented triads have a plus sign (+). You may see other abbreviations in other contexts (a more exhaustive list is given in the Chord Symbols chapter).

Within major and minor keys, triads have particular qualities that correspond to scale degree. These are the same in every major and minor key, which makes memorizing them useful.

Triads are identified by their root, quality, and inversion.

A chord is any combination of three or more pitch classes that sound simultaneously. This chapter focuses on triads—three-note chords whose notes can be stacked into thirds.

Triads

The three notes of a triad can always be arranged in thirds. Example 1 shows two triads, each written both melodically and harmonically. The first triad is on three adjacent spaces, while the second triad is on three adjacent lines. A triad can always be "stacked" so that its notes are either on all lines or all spaces. When a triad is stacked in its most compact form (measures 2 and 4 of Example 1), it looks like a snowperson (see Example 2). Just as a snowperson consists of a bottom, middle, and head, a triad consists of lowest, middle, and upper notes.

Example 1. Two triads, shown melodically and harmonically.

Example 2. A snowperson.

[](https://viva.pressbooks.pub/app/uploads/sites/12/2019/05/Screen-Shot-2020-08-17-at-1.39.09-PM.png) Example 3. A triad with the root, third, and fifth labeled.

Colloquially, when a triad is stacked in this fashion, we might call this "snowperson form," but the official term is root position; this is explored more in the chapter titled Inversion and Figured Bass. As Example 3 shows, the lowest note of a triad is called the root, the middle note is called the third (a generic third above the root), and the highest note is called the fifth (a generic fifth above the root).

Triadic Qualities and Listening to Triads

There are four qualities of triad—major, minor, diminished, and augmented—which are determined by the quality of the intervals from the root to the third and the root to the fifth. These qualities are labeled in Example 4: triad qualities are shown above the staff, the quality of the fifth to the root is given in red to the left of the triad, and the quality of the third is given in blue to the right of the triad. Augmented triads are shown last because the other three types are more common in most classical and popular music.

Note that triads are named for certain important intervals they contain:

Major and minor triads are named for the quality of their third. (Both have perfect fifths.)

Diminished and augmented triads are named for the quality of their fifth:

A diminished triad's fifth is diminished. (Its third is minor.)

An augmented triad's fifth is augmented. (Its third is major.)

Listen carefully to the different qualities of triad in Example 4. It is common to pair expressive qualities with triads when learning what they sound like. You might think of major triads as sounding "happy," minor triads as "sad," diminished triads as "scary," and augmented triads as having a "fantasy" or "mystical" sound.

Example 4. Different qualities of triads.

Chord Symbols

Chord symbols for triads include the letter name of the root and an indication of the triad’s quality, and sometimes the pitch class of the bass voice (meaning the lowest note in the chord, not any particular instrument or voice type).

A chord symbol begins with a capital letter (and, if necessary, an accidental) denoting the root of the chord. That letter is followed by information about a chord’s quality. Open Music Theory will use the following abbreviations.You may see other abbreviations in other contexts (a more exhaustive list is given in the Chord Symbols chapter).

Major triad: no quality symbol is added

Minor triad: lowercase “mi”

Diminished triad: superscript circle (o)

Augmented triad: plus sign (+)

For example, the chord symbols C, Cmi, Co, and C+ mean a C major triad, C minor triad, C diminished triad, and C augmented triad, respectively. If the root of the chord has an accidental, include it: for example, B♭mi is the chord symbol for a B♭ minor triad, and F♯o is the chord symbol for an F♯ diminished triad.

Finally, if a pitch class other than the chord root is the lowest note in the chord, a slash is added, followed by a capital letter denoting the pitch class in the bass. This topic will be explored more in the chapter titled Inversion and Figured Bass. Example 5 first shows C major and C minor triads with their chord symbols (C and Cmi). It then shows how the chord symbol for the C minor triad changes when a note other than C is on the bottom: when E♭ is the lowest note, the chord symbol is Cmi/E♭, and when G is the lowest note, the symbol is Cmi/G.

Example 5. Four triads are shown with chord symbols.

Triad Qualities in Major and Minor

Any note of the major scale can be the root of a triad.