TonalityGUIDE - Tonal music basic theory for Undergraduates
  Startcentre  |  Reference Guide  

The V in a perfect cadence (V - I) is often intensified by the addition of a seventh. This so-called dominant seventh very strongly defines the key of a passage because no other diatonic seventh chord has the characteristic major third, perfect fifth and minor seventh above the root. Dominant sevenths almost always resolve in the way shown in the example. An exception is the interrupted cadence and the German augmented sixth chord which, although it is 'spelt' differently, sounds the same as a dominant seventh.