interval
B perfect fourth
BlowerEupperP45 half steps
Five half steps. Turned upside down it becomes a perfect fifth.
On the keyboard
What is true of it
B up a perfect fourth is E: 5 half steps, and 4 letters counting both ends.
Turn it upside down — put the B 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 B
B → Cminor second · dissonanceB → C♯major second · dissonanceB → Dminor third · imperfect consonanceB → D♯major third · imperfect consonanceB → E♯augmented fourth · dissonanceB → Fdiminished fifth · dissonanceB → F♯perfect fifth · perfect consonanceB → Gminor sixth · imperfect consonanceB → G♯major sixth · imperfect consonanceB → Aminor seventh · dissonanceB → A♯major seventh · dissonance