Seventh Chords

A seventh chord is a four-note chord stacked in thirds. Think of it as a triad with another note on top. This top note is the seventh above the root, hence the name seventh chord.

Like triads, the notes of a seventh chord are named according to their interval above the root: the root, the third, the fifth, and the seventh.

There are five qualities of seventh chords. Like triads, the quality is determined by the combination of intervals (thirds) that make up the chord:

• Major Seventh (M7): Major triad + major seventh (4 + 3 + 4 half steps)
• Dominant Seventh (7): Major triad + minor seventh (4 + 3 + 3 half steps)
• Minor Seventh (m7): Minor triad + minor seventh (3 + 4 + 3 half steps)
• Half-Diminished Seventh (o\7): Diminished triad + minor seventh (3 + 3 + 4 half steps)
• Fully-Diminished Seventh (o7): Diminished triad + diminished seventh (3 + 3 + 3 half steps)

The four inversions of a seventh chord are as follows:

• Root position: The root is in the bass. When in root position, the pitches of a seventh chord are on consecutive lines or spaces.
• First inversion: The third is in the bass.
• Second inversion: The fifth is in the bass.
• Third inversion: The seventh is in the bass.

When presented with an unknown seventh chord, follow these systematic steps to determine the root, quality, and inversion:

• Determine the root by stacking the chord members in thirds. Look for the interval of a second in inverted seventh chords; the upper note of that second is always the root! Rearrange all four pitches onto consecutive lines or spaces. The lowest note of the stack is the root.
• Determine the quality by measuring the semitone intervals between the root, third, fifth, and seventh in root position. Match the interval formula with the five qualities (M7, 7, m7, o\7, o7).
• Determine the inversion by observing which chord member is in the bass voice. If the root is in the bass, it is root position; if the third is in the bass, first inversion; if the fifth is in the bass, second inversion; if the seventh is in the bass, third inversion.