What is the major key that has one flat?

F major is the major key that has one flat in its key signature. In music theory, the key of F major consists of the notes F, G, A, B♭, C, D, and E. The presence of one flat indicates that the B is lowered by a half step to B♭, which is a defining characteristic of this key.

Understanding key signatures is critical when playing and composing music. The Circle of Fifths is a helpful tool for visualizing the relationships among different keys; F major is located to the left of C major and to the right of B♭ major, further reinforcing that F major is the key that features a single flat. This knowledge can assist musicians in quickly identifying the key they are working in, which influences the overall sound and emotional context of the music.