key
tonic
mode
key signature
order of sharps or flats
number of sharps or flats
Musicians use the term, key, to identify the tonic and mode of a piece or passage of music. If a composition is said to be “in the key of F major,” for example, this means that its tonic, or tonal focus, is the note F in the major mode, i.e., it essentially uses the notes of the F major scale.
There are fifteen major keys corresponding to the fifteen major scales. Each major key has a unique key signature, a standard arrangement of the sharps or flats used to notate the corresponding major scale. For example, an A-flat major scale uses flats on the notes A, B, D, and E. The key signature for the key of A-flat major consists of these four flats arranged on the staff in this order: B, E, A, and D. Example 7-1 illustrates the relationship between scale and key signature in A-flat major.
Example 7-1
It is important for any musician to quickly recognize and understand key signatures since most music is notated within a key signature. And, as you will see in Lesson 8, key signatures can be used in scale spelling as well. To learn key signatures, you must first learn the order of sharps or flats and the number of sharps or flats in each key.