interval
E perfect fourth
ElowerAupperP45 half steps
Five half steps. Turned upside down it becomes a perfect fifth.
On the keyboard
What is true of it
E up a perfect fourth is A: 5 half steps, and 4 letters counting both ends.
Turn it upside down — put the E on top — and it becomes a perfect fifth. The two numbers always add to nine, and the two sizes to twelve.
It is a perfect consonance.
Every interval on E
E → Fminor second · dissonanceE → F♯major second · dissonanceE → Gminor third · imperfect consonanceE → G♯major third · imperfect consonanceE → A♯augmented fourth · dissonanceE → B♭diminished fifth · dissonanceE → Bperfect fifth · perfect consonanceE → Cminor sixth · imperfect consonanceE → C♯major sixth · imperfect consonanceE → Dminor seventh · dissonanceE → D♯major seventh · dissonance