What is a key in music?

At the very start of your journey to learn music theory, the most important concept to get under your belt is that of keys. At first, the concept may be a little confusing, but stick with it because understanding keys will kick start your grasp of bass guitar theory.

The key of a piece of music refers to the major or minor scale it revolves around. Major keys are based on major scales. Minor keys are based on minor scales.

For example, a song played in the key of C major revolves around the seven notes of the C major scale which are highlighted in red in the table below.

Notes making up the song, melody, chords and bass line for a piece of music in the key of C major are all picked from the group of notes in red - the C major scale.

In the same way, a song in the key of A minor uses the notes of the A minor scale which are highlighted in red in the table below.

The root note of a key is the pitch which defines its tonal center. As with the root note of a chord, the root note of a scale is the note on which the scale is built. The root note of the C major scale is C. The root note of the A minor scale is A. Another word for the root note of a scale is the tonic.

In music, the tonic is where maximum harmonic resolution occurs. The tonic is a key’s center and moving to other notes in the key and returning to the tonic creates musical tension and resolution that is pleasing, or harmonious, to the ear. When you’re next listening to a piece of music, try and identify the key and listen out for the way the music creates tension and resolution to the tonic.

If a note is not part of the key, it is said to be outside of the key. It is certainly possible to use outside notes, but usually most of the notes in a song are taken from the key. If you overuse outside notes, the music may sound too discordant and unpleasant to the ear. That said, skilled musicians have found many uses for outside notes, for example the creation of stronger tension and resolution. Bass players in particular may use outside notes to link chords together in a walking bass line.

There are 12 major scales so there are 12 major keys. Similarly, there are 12 minor scales and so 12 minor keys. That makes 24 keys in all.

Of the major keys, three of them can be named 2 different ways, even though they’re the same notes and so this means there are actually 15 ways a major key might be notated.

For example, the G♭ and F# are the same note, but notated differently. The keys of G♭ major and F# major contain the same notes, but again, are notated differently according to the musical context.

In the same way, there are 15 different ways to notate minor keys. This means there are 24 keys, but 30 ways to notate them.

If you’d like to learn more about keys, members at Scott’s Bass Lessons have access to a course called ‘Functional Theory’ that will teach you everything you need to know about arpeggios, chord tones and scales for the bass guitar.

To become a member, just go to the course page and click on the ‘free trial’ button. This course alone is worth the price of a year’s membership, but you will also find a HUGE number of other courses as well as gain access to our community where you can ask questions of other members and our pro bass mentor team.