The concept of keys in music is important to understand. The idea is a bit abstract and can be confusing, even mystifying, in the beginning. With experience the concept will become more and more clear. You might consider rereading this lesson from time to time until you solidfy your understanding of this essential musical concept.
What is a Key in Music?
In music a key is the major or minor scale around which a piece of music revolves. A song in a major key is based on a major scale. A song in a minor key is based on a minor scale.
A song played in the ‘key of C major’ revolves around the seven notes of the C major scale C, D, E, F, G, A, and B. That means the fundamental notes making up the song’s melody, chords, and bassline are all derived from that group of notes.
A song in the ‘key of F major’ uses the notes of the F major scale F, G, A, Bb, C, D, and E.
Similarly, a piece of music can be in a minor key and revolve around a natural minor scale. For example, a song in the ‘key of D minor’ uses the notes of the D minor scale D, E, F, G, A, Bb, and C.
Any major scale or natural minor scale can serve as a key for a piece of music.
The Center of It All - The Tonic
The root note of the key acts as the center of the key. Similar to the root notes of chords, the root note of a scale is the note on which a scale is built. For example, the root of the C major scale is C. The root note of an Eb minor scale would be Eb. When speaking of keys, the root note of the key is called the tonic (pronounced TAWN-ik).
I think of keys and the tonic like gravity on Earth. All objects are constantly pulled toward Earth until they come to a state of rest on its surface. Objects can move away from Earth, but eventually come back down.
When you play music, the music is constantly being pulled toward the tonic, or root of the key, wanting to come to a state of rest or completion. The tonic is the most resolved note in a key. The tonic is a key’s center.
Moving away from and back to the tonic resting point of the key is partly what makes music interesting and why it has a pleasing effect on us. Continuing the gravity analogy, music momentarily defies gravity, but then comes back down. It’s exciting much like a pole-vaulter, basketball player, or juggler might be.
When music has this centered sound to it, it is said to be tonal (pronounced TOE-nul), or possessing tonality. Almost all music to which we listen is tonal. When a piece of music lacks a tonal center it is said to be atonal (pronounced AY-toe-nul). Most people don't like the sound of atonal music.
Listen for the Tonic
As you listen to music, try to pay attention to these concepts of tonality and resolution. Although points of resolution occur all throughout a song, you will most noticeably hear it at the end of a song. Most songs finish on the tonic of the key to make the song sound complete or finished. It’s a very natural sound to expect and it will sound strange when you don’t hear it. When the end of a song goes unresolved it often has a comical effect. This effect is possible because of everyone’s natural sense of tonality.
There are a couple of audio examples of the sense of tonality.
Can a Piece of Music Only Use Notes Within the Key?
Notes not in the scale are considered to be outside of the key. Outside notes can be (and often are) used, but the bulk of the notes will still center around the notes of the key and the key’s tonic. If outside notes are used improperly it’s possible to throw off a song’s tonality and create an unpleasant effect.
Skilled musicians and composers have learned to use these outside/off key notes without upsetting the tonality of the music. Outside notes occur in most styles of music to some degree. You will hear the use of outside notes heavily in many jazz solos. Or, you might find them used in heavy metal riffs. Or, you may find them in a simple pop song.
How Many Music Keys Are There?
Since there are 12 major scales, there are 12 major keys. Likewise, there are 12 minor scales and, therefore, 12 minor keys. So there are 24 keys all together.
Three of the major keys can be named 2 different ways one way with sharp note names, and the other way with flat note names. This results in 15 different major key spellings.
As an example, the keys of Gb major and F# major contain the exact same notes. The former is spelled using flat note names (Gb, Ab, Bb, Cb, Db, Eb, and F), while the latter is spelled with equivalent sharp note names (F#, G#, A#, B, C#, D#, and E#). There will be times when choosing one spelling over another is preferable. (More on that later.)
In the same way, there are 15 different minor key spellings.
In total, there are 24 keys and 30 ways to spell them. In the next few lessons covering the circle of 5ths, I will show you how you can start memorizing all 30 key spellings. It sounds far scarier than it is, but it will take some effort.