Key of F

F major

Relative key	D minor
Parallel key	F minor
Dominant key	C major
Subdominant	B♭ major
Component pitches
F, G, A, B♭, C, D, E

F major (or the key of F) is a major scale based on F, with the pitches F, G, A, B♭, C, D, and E. Its key signature has one flat, B♭.

F major's relative minor is D minor, and its parallel minor is F minor.

F major is the home key of the English horn, the basset horn, the horn in F, the trumpet in F and the bass Wagner tuba. Thus, music in F major for these transposing instruments is written in C major. Most of these sound a perfect fifth lower than written, with the exception of the trumpet in F which sounds a fourth higher. (The basset horn also often sounds an octave and a fifth lower.)

...
Wikipedia