Key Signatures are a very important concept to understanding the overall structure and form of songs and compositions. Key signatures contain a great deal of information that helps composers write their music, and helps musicians understand it faster and more in-depth. In this chapter, both sharp and flat key signatures will be explored for both major and minor scales. Also, the circle of fifths and fourths will be explored to show how they will help utilize the full potential of key signatures.

Major Keys

The key signatures used in major keys are split in half between sharp keys and flat keys. These major keys share the same notes as major scales. It is a good idea to look at the first line of a song, before the time signature, to see what key the song is in. This will help indicate which notes will be most present in the song. Some songs will use the notes in a key signature throughout the whole song, while other songs will add notes outside that key signature or even change key signatures.

This table 1 below shows all the major keys, their notes, and a staff line picture showing which notes are sharp and which are flat. Remember, the notes in the key signature are the same as the corresponding major scale. The key of C shares the same notes as the C major scale.

Minor Keys

This next table 2 shows all the minor key signatures, their notes, and a staff line picture showing which notes are sharp and which are flat. Study and memorize these key signatures as well.

Step Numbers Determine Key Center

The Key, or tonic center of a song can be determined by looking at the beginning of a song before the time signature, but they can be determined by scale step numbers as well. For example, a song using the chord progression C-F-G can be compared to the harmonized major scale (I-ii-iii-IV-V-vi-vii), in which three major chords match the key of C, I-IV-V chords (C-Dm-Em-F-G-Am-Bdim). Because major chords can only fall under the I, IV, and V steps, the key of C is the only key that exactly matches the chord progression C-F-G. By testing the key of G chords (G-Am-Bm-C-D-Em-F#dim), the I-IV-V chords are G-C-D. Testing the key of F chords (F-Gm-Am-Bb-C-Dm-Edim), the I-IV-V chords are F-Bb-C. Here is one more example: A-G#dim-F#m. Keeping in mind the seventh step is always diminished (?-vii-?), the I step is always played as a major chord type and is a half step from the seventh step ( I-vii-?). This means the A chord could not be a IV or V step chord. Consequentially, the F#m chord fits the vi step best because the vi step is a whole step from the vii step. Furthermore, this means the F#m chord could not be a ii or iii step chord. As such, the A-G#dim-F#m (I-vii-vi) chord progression is in the key of A.

These examples are a great exercise to practice determining what key a song is played in. Begin practicing simple chord progressions like the examples above. Then, create more complex chord progressions, keeping in mind some chords in a chord progression may not come directly from the key signature or harmonized major scale. By studying the song’s chord progression and listening for the tonic cneter, a song’s key can be quickly found.

Key Signature Builder

This exercise shows all Major Key Signatures, along with the notes in that key. Simply select the key from the listbox below.