Seventh Chord
A seventh chord is formed by adding an additional note to a traditional three-note basic chord. They are called seventh chords because this extra note is 7 scale degrees higher than the root. This added note creates a richer and more complex sound. Like basic chords, seventh chords are built from the notes of the major scale and therefore come in several different qualities that inherit and expand upon their basic counterparts.
Below, you can listen to all seventh chords formed from the major scale.
The basic I and IV chords are major chords, and when extended to seventh chords, they become major sevenths, written as I7 and IV7.
The basic ii, iii, and vi chords are minor chords, and they become minor sevenths, written as ii7, iii7, and vi7.
The basic V chord (containing scale degrees 5, 7, and 2) is a major chord, but its 7th (scale degree 4) creates a smaller interval than the 7ths of the other major chords, giving it a unique sound. Written as V7, this seventh chord has what is called a dominant quality. This dominant quality strengthens the V chord’s already strong pull back to I, making it an even stronger cadence chord.