Intervals · Step 8
Fourth, fifth and the tritone
Past the third come three intervals a semitone apart, and they could not sound more different. Five semitones is a perfect fourth: the opening of “Here Comes the Bride”, steady and a little formal. Seven is a perfect fifth: the first two notes of the Star Wars theme, wide and stable, the most consonant interval after the octave. And between them sits six semitones, the tritone: the start of “Maria” from West Side Story, tense and unresolved, wanting to move.
The fourth and the fifth are called perfect because they come in one size only; there is no major or minor fifth. The tritone is what you get when you push either of them by a semitone, and its restlessness drives a great deal of harmony. Hear the three and pick.