fs key

The main or central note of a piece of music (or part of a piece of music). Each key has its own scale, beginning and ending on the note that defines the octave of the next scale. The key of C-major uses a scale that starts on C and uses only the white keys of the piano. In a piece composed in the key of C, the music is likely to end on the note C, and certain combinations of notes based on C will predominate.