Dominant seventh chord

Why it sounds so decisive

The fifth degree of C major is G major: G–B–D. The B in it is the leading tone. Add the minor seventh, the F, and G7 arises, and this chord contains two notes that push in opposite directions at the same time. The B wants to go a semitone up to C, the F a semitone down to E. Between B and F lies a tritone. If you resolve both at once, you land on C and E, two of the three notes of the C major triad. The chord therefore does not resolve arbitrarily, but because two semitone moves head for the same goal.

That is why the cadence G7–C is so inescapable that it forms the ending of very many pieces of Western music between 1650 and 1900. You can hear it: the chord sounds “unfinished”, it wants to go on. This built-in pull makes it the engine of countless closing phrases, from Bach to today's pop song. In functional terms it is the dominant, particularly strong as a seventh chord (V7).

The dominant seventh in blues and jazz

Practically every blues piece begins or ends with a seventh chord. The minor seventh is the typical blue note there. In jazz it is a central note in practically every ii–V–I pattern.

Common mistakes

• Confusing it with the major seventh chord: G7 has the minor seventh, Cmaj7 the major.
• Leading the leading tone downwards: B goes upwards to C.
• Leaving the seventh unresolved when you want an ending: The F must go down to E.