Piano chord chart: all chords and inversions on the keyboard

Definition

A chord is the sound of two or more notes being played at the same time. The term derives from "accord", which became "cord" in Middle English. The original meaning was an agreement or harmonious sound. In the 17th century, the spelling was changed to "chord" to prevent confusion with "cord".

Until the Middle Ages, harmony was any combination of two notes. In the Renaissance, the simultaneous sound of three notes began to be understood as the working definition of harmony. An arpeggio is a broken chord where each note is sounded successively instead of simultaneously. Chords can also be implied by melodies.

A chord progression is a collection of harmonies with a specific destination or purpose, such as reinforcing the tonic or modulation to a new pitch center. Chord progressions are common in Western music. Homophonic textures where the melody and harmony generally move in unison are considered the standard practice in classical music and remain central to music instruction. The study of harmony involves chords and progressions and the principles of connection that govern them.

Structure

Just as scales derive from the harmonic series, the major chord is likewise formed by overtones 4, 5, and 6. The next overtone creates a seventh chord. A common triad has three notes: the root, third, and fifth. The intervals are identified by their distance from the root of the chord. The notes that form a chord are sometimes called members or factors.

Continuing up in thirds yields a seventh, ninth, eleventh, and thirteenth before returning to the root again. Complex sonorities larger than a tetrad are sometimes called polychords because they can be seen as combinations of two different chords. Extended chords are one of the central characteristics of jazz harmony.

Chords are identified by their intervals. The four basic triad qualities are major, minor, diminished, and augmented. Major and minor chords derive from the quality of their thirds. Diminished and augmented chords describe the quality of the fifth. Additional intervals like sevenths are also described by their quality in relation to the root.

Composers began expanding tonality beyond the common practice and often structured chords in fourths and fifths. They were more tonally ambiguous, enabling new patterns for music. Chords also shrunk to tone clusters made of small intervals like seconds. The resulting sound mass was a common feature in the 20th century. Microtonal chords are also used by many contemporary composers.

Theorists began to analyze the structure of chords in the 16th century. Jean-Philippe Rameau developed the nomenclature for chord inversion that is still in use today.

Root position is when the lowest note of a chord is the root, regardless of how the other members are arranged above it. The chord is considered inverted when the root is not the lowest voice. When the third is the lowest sounding pitch, the chord is in first inversion. The second inversion puts the fifth in the bass and was widely seen as dissonant, even as composers put it into frequent practice.

Root position and inverted chords

A chord is in root position if its root is the lowest note. This is sometimes known as the parent chord of its inversions. For example, the root of a C-major triad is C, so a C-major triad will be in root position if C is the lowest note and its third and fifth (E and G, respectively) are above it – or, on occasion, do not sound at all.

The following C-major triads are both in root position, since the lowest note is the root. The rearrangement of the notes above the bass into different octaves (here, the note E) and the doubling of notes (here, G), is known as voicing – the first voicing is close voicing, while the second is open.

In an inverted chord, the root is not the lowest note. The inversions are numbered in the order their lowest notes appear in a close root-position chord (from bottom to top).

As shown above, a C-major triad (or any chord with three notes) has two inversions:

1. In the first inversion, the lowest note is E – the third of the triad – with the fifth and the root stacked above it (the root now shifted an octave higher), forming the intervals of a minor third and a minor sixth above the inverted bass of E, respectively.
2. In the second inversion, the lowest note is G – the fifth of the triad – with the root and the third above it (both again shifted an octave higher), forming a fourth and a sixth above the (inverted) bass of G, respectively.

Overview

In music, a triad is a set of three notes (or "pitch classes") that can be stacked vertically in thirds. Triads are the most common chords in Western music.

When stacked in thirds, notes produce triads. The triad's members, from lowest-pitched tone to highest, are called:

• the root
• Note: Inversion does not change the root. (The third or fifth can be the lowest note.)
• the third – its interval above the root being a minor third (three semitones) or a major third (four semitones)
• the fifth – its interval above the third being a minor third or a major third, hence its interval above the root being a diminished fifth (six semitones), perfect fifth (seven semitones), or augmented fifth (eight semitones). Perfect fifths are the most commonly used interval above the root in Western classical, popular and traditional music.

Some 20th-century theorists, notably Howard Hanson, Carlton Gamer, and Joseph Schillinger expand the term to refer to any combination of three different pitches, regardless of the intervals. Schillinger defined triads as "A structure in harmony of but three parts; conventionally, but not necessarily, the familiar triad of ordinary diatonic harmony." The word used by other theorists for this more general concept is "trichord". Others use the term to refer to combinations apparently stacked by other intervals, as in "quartal triad"; a combination stacked in thirds is then called a "tertian triad".

The root of a triad, together with the degree of the scale to which it corresponds, primarily determine its function. Secondarily, a triad's function is determined by its quality: major, minor, diminished or augmented. Major and minor triads are the most commonly used triad qualities in Western classical, popular and traditional music. In standard tonal music, only major and minor triads can be used as a tonic in a song or some other piece of music. That is, a song or other vocal or instrumental piece can be in the key of C major or A minor, but a song or some other piece cannot be in the key of B diminished or F augmented (although songs or other pieces might include these triads within the triad progression, typically in a temporary, passing role). Three of these four kinds of triads are found in the major (or diatonic) scale. In popular music and 18th-century classical music, major and minor triads are considered consonant and stable, and diminished and augmented triads are considered dissonant and unstable.

When we consider musical works we find that the triad is ever-present and that the interpolated dissonances have no other purpose than to effect the continuous variation of the triad.

Construction

Triads (or any other tertian chords) are built by superimposing every other note of a diatonic scale (e.g, standard major or minor scale). For example, a C major triad uses the notes C–E–G. This spells a triad by skipping over D and F. While the interval from each note to the one above it is a third, the quality of those thirds varies depending on the quality of the triad:

• major triads contain a major third and perfect fifth interval, symbolized: R 3 5 (or 0–4–7 as semitones)
• minor triads contain a minor third, and perfect fifth, symbolized: R ♭3 5 (or 0–3–7)
• diminished triads contain a minor third, and diminished fifth, symbolized: R ♭3 ♭5 (or 0–3–6)
• augmented triads contain a major third, and augmented fifth, symbolized: R 3 ♯5 (or 0–4–8)

The above definitions spell out the interval of each note above the root. Since triads are constructed of stacked thirds, they can be alternatively defined as follows:

• major triads contain a major third with a minor third stacked above it, e.g, in the major triad C–E–G (C major), the interval C–E is major third and E–G is a minor third.
• minor triads contain a minor third with a major third stacked above it, e.g, in the minor triad A–C–E (A minor), A–C is a minor third and C–E is a major third.
• diminished triads contain two minor thirds stacked, e.g., B–D–F (B diminished)
• augmented triads contain two major thirds stacked, e.g., D–F♯–A♯ (D augmented).

Triads appear in close or open positions. "When the three upper voices are as close together as possible, the spacing is described as close position or close harmony. [...] The other arrangements [...] are called open position or open harmony."

A seventh chord is a chord consisting of a triad plus a note forming an interval of a seventh above the chord's root. When not otherwise specified, a "seventh chord" usually means a dominant seventh chord: a major triad together with a minor seventh. However, a variety of sevenths may be added to a variety of triads, resulting in many different types of seventh chords.