Scale (music)
Scales use either just sharps or just flats when choosing between the two names for the same note, when this is possible. In a scale of seven different notes, each letter is used only once. This means that some scales have one or two notes named with a sharp or a flat even though they are played by white keys. In the C♯ Major scale, for example, all the notes have names with a sharp: C♯, D♯, E♯, F♯, G♯, A♯, B♯, C♯. In this scale, E♯ is the name for the note played by the key that plays F and the B♯ is the name for the note played by the key that plays C. The same notes are used in the D♭ Major scale, but they all have different names: D♭, E♭, F, G♭, A♭, B♭, C, D♭.