A seventh chord adds one extra note to a basic three-note triad, creating a richer and more expressive sound. In music theory, this extra note is called the seventh because it is seven letter names above the chord root. For example, a C major triad uses C, E, and G, while a Cmaj7 chord adds B.
Seventh chords matter because they help composers and performers create color, tension, smooth motion, and emotional depth.
Key Facts
- A triad has three notes: root, third, and fifth.
- A seventh chord has four notes: root, third, fifth, and seventh.
- C major triad = C, E, G.
- Cmaj7 = C, E, G, B.
- A major seventh interval is 11 semitones above the root.
- A dominant seventh chord uses a major triad plus a minor seventh, such as C7 = C, E, G, Bb.
Vocabulary
- Triad
- A triad is a three-note chord built from a root, a third, and a fifth.
- Seventh Chord
- A seventh chord is a four-note chord made by adding a seventh above the root to a triad.
- Root
- The root is the main note that gives a chord its name.
- Major Seventh
- A major seventh is an interval 11 semitones above the starting note.
- Chord Color
- Chord color is the emotional or expressive quality added by the notes and intervals in a chord.
Common Mistakes to Avoid
- Calling every seventh chord major seventh, which is wrong because Cmaj7, C7, Cm7, and Cm(maj7) all use different thirds and sevenths.
- Forgetting to count letter names when finding the seventh, which can lead to spelling Cmaj7 as C, E, G, Cb instead of C, E, G, B.
- Confusing C7 with Cmaj7, which is wrong because C7 has Bb while Cmaj7 has B natural.
- Thinking the seventh must always be the highest note, which is wrong because chord tones can be rearranged into different inversions.
Practice Questions
- 1 Write the notes in a G major triad, then add the major seventh to make Gmaj7.
- 2 How many semitones are between C and B in a Cmaj7 chord, and how many semitones are between C and Bb in a C7 chord?
- 3 A song changes from a plain C major chord to Cmaj7 at the end of a phrase. Explain how adding B changes the sound compared with using only C, E, and G.