The keyboard black keys are significant in that they are the sign-posts we depend on to find our way around the keyboard. But the keyboard black keys also have another very important roll in that they allow us to play half-tones ascending and half-tones descending. These half-tones ascending or descending give a single black key two different names, depending on whether the tone is rising or falling.
Ascending to the Right :
Using the illustration below, let’s talk about the naming of the black keys. The black key to the right of C is called C# (C sharp) the tone rises from C to C#, the black key to the right of D is D#, the pitch rises, the black key to the right of F is F#, so …all the black keys to the right of the white keys are called sharps… the tone is rising by a half-tone.
Descending to the left:
Now let’s talk about the reverse. When the tone or pitch of the black key is lowered (to the left) of the white key, the black key is called a flat (b). Therefore the black key to the left of D is Db, to the left of E is Eb, to the left of G is Gb and so on. The black keys to the left of the white keys are called flats. The tone is lowered by a half-tone.
Keys are called sharps when pitch is rising and flats when pitch is lowered, in reality that gives each black key 2 different names ………. strange but true.