interval
F perfect fourth
FlowerB♭upperP45 half steps
Five half steps. Turned upside down it becomes a perfect fifth.
On the keyboard
What is true of it
F up a perfect fourth is B♭: 5 half steps, and 4 letters counting both ends.
Turn it upside down — put the F 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 F
F → G♭minor second · dissonanceF → Gmajor second · dissonanceF → A♭minor third · imperfect consonanceF → Amajor third · imperfect consonanceF → Baugmented fourth · dissonanceF → C♭diminished fifth · dissonanceF → Cperfect fifth · perfect consonanceF → D♭minor sixth · imperfect consonanceF → Dmajor sixth · imperfect consonanceF → E♭minor seventh · dissonanceF → Emajor seventh · dissonance